This was what happened to me this pregnancy. I developed a slow leak - very different from last time when my waters broke completely a few hours before labor started. In this case, it was a very slow leak, and labor didn't actually start until 2 1/2 days after it happened. My midwife guessed that it was a leak on the top of the bag, and she also told me that it's possible for it to reseal (though mine never did). It started on a Saturday night, and I called her that night.
I would definitely call - even if it's a small leak, that's something they would want to know about. Mine sent her assistant over the next day to make sure it was amniotic fluid (she said sometimes the baby can be pushing against the bladder without me realizing it and it could have been urine) and to check heart tones, etc. She also wanted me to rest, not go out as much, avoid sex (and she avoided internal exams for hte same reason, to decrease risk of infection), and generally be a bit more careful than i would have been without a rupture, however small.
Mine was also a CNM, but a home birth one - she never mentioned induction, and wasn't overly worried about infection, which i was grateful for. This might be different with a hospital practice, which may have certain rules about inducing after a certain amount of time, or with different midwives, or if you're GBS positive. So I guess you could use your own judgment about how likely your midwife is to want to push interventions, but I think she'd still want to know about it.