It was probably smegma. Nothing wrong with washing it off, though, smegma is a good thing:
"Smegma is probably the most misunderstood, most unjustifiably maligned substance in nature. Smegma is clean, not dirty, and is beneficial and necessary. It moisturizes the glans and keeps it smooth, soft, and supple. Its antibacterial and antiviral properties keep the penis clean and healthy. All mammals produce smegma. Thomas J. Ritter, MD [co-author of Say No to Circumcision] underscored its importance when he commented, 'The animal kingdom would probably cease to exist without smegma.'" ("Where Is My Foreskin? The Case Against Circumcision," by Paul M. Fleiss, MD, Mothering, Winter 1997)
"Infant Smegma: Skin cells from the glans of the penis and the inner foreskin are shed throughout life. This is especially true in childhood; natural skin shedding serves to separate the foreskin from the glans. Since this shedding takes place in a relatively closed space -- with the foreskin covering the glans -- the shed skin cells cannot escape in the usual manner. They escape by working their way to the tip of the foreskin. These escaping discarded skin cells constitute infant smegma." / "Adult Smegma: ... Adult smegma serves as a protective, lubricating function for the glans." ("Care of the Uncircumcised Penis," American Academy of Pediatrics, 1984)
"An infant's glans is very delicate and can be seriously irritated by urine. The foreskin acts as a cover for the glans and produces smegma for a protective coating." (p. 55) / "As to smegma, the normal secretion produced under the foreskin, Gairdner claimed that this substance protects the glans. This is particularly important if wet diapers are left on too long, since decomposition of the urine can cause irritation of the glans if it is not coated with smegma." (p. 64) / "[T]here is not a shred of evidence to support to theory that smegma is carcinogenic." (p. 91) / "All animals produce smegma, and none is circumcised. When mammals reproduce, smegma is deposited. If smegma contained a carcinogen or even an irritant, then the propagation of the species would be jeopardized. No such phenomenon exists." (p. 106) (Circumcision: An American Health Fallacy, by Edward Wallerstein, Springer Publishing Co., 1980)
"Several researchers have tried to prove that smegma causes cancer; all have failed. Not only is smegma not harmful, it is actually beneficial, serving as a protective coating and lubricant for the glans." ("The Circumcision Decision," by Edward Wallerstein, Pennypress, Inc., 1980)
"This process of rationalization has culminated in the supposed relationship between the husband's foreskin and cancer of the genitals--one of the greatest hoaxes in the history of medicine. The theory is that the uncircumcised penis, because it may generate a waxy substance called smegma, can produce cancer of the penis and cancer of the cervix (neck of the womb) ... Further evidence that circumcision is not linked with cancer comes from tests of human smegma. In 1942, the National Cancer Institute conducted careful experiments and found that smegma had no carcinogenic effect whatsoever. This test was duplicated in 1963 on a more extensive scale by Dr. D. G. Reddy and others, with the same conclusions. Negative results have also been obtained in a number of other experiments (Circumcision in Infancy, Charles Weiss, M.D., Clinical Pediatrics, 1964)." ("The Unkindest Cut of All," by John M. Foley, MD, Fact, July 1966)
"Analogous to tears, smegma is the compilation of secretions by ectopic sebaceous glands located in the prepuce, the seminal secretions of the Cowper's gland and the prostate, the mucin content of the secretions of the urethral glands, and the sloughed epithelial cells. It provides the necessary mucosal lubricant and moisturizer and is rich in sexual pheromones. The prepuce normally prevents detection of this phenomenally charged scent until the glans is exposed at the time erection takes place." (Routine Neonatal Circumcision: An Update, by Robert S. Van Howe, MD)
"Is smegma useful? Yes, certainly. It lubricates the cavity between the foreskin of the penis and the glans, thus allows smooth movement between them during intercourse ... Nature has ... provided a natural ointment, smegma, to ensure easy lubrication and protect this delicate region of the male genital organ. / To secure its even distribution, smegma is formed from the whole inner surface of the foreskin cavity ... Smegma production ... is concentrated in the cells of innumerable small prominences, minute microscopic protrusions of various shapes and sizes found on the inner surface of the foreskin cavity ... Sexual intercourse becomes a regular feature of life [in adulthood] and the function of smegma assumes its full value ... Freshly formed smegma ... is a wholesome lubricant--making for ease in erection and smoothness in sexual intercourse." ("How Smegma Serves the Penis," by Joyce Wright, MD, Sexology, 10/70, pp. 50-53)
"If allowed to accumulate for several years, smegma might possibly cause some irritation. But, even this is doubtful." (Modern Sex Techniques, by Robert Street, Lancer Books, NY, 1959, p. 154)
http://www.foreskin.org/smegma.htm
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