TMI - specific details here for stretched out blood vessels 'down there' on the perineum: Hemorrhoids and vaginal varicose veins are closely related, blood stretching out the vein as the result of the extra weight put on our perineum. For anal varicose veins (hemorrhoids) they can be gently 'pushed back in' to the rectum (bath or shower is perhaps the best place to do this - as can personal lubricant) starting at the furthest point away from the anus and pushing toward inside. Relaxing and constricting the anus can help provide movement to push the bulge inside, and once in, sometimes the vein can be pushed 'down' even a little more to reduce its swelling. For very large bulges, gentle direct pressure on top of the bulge toward the anus with a few fingertips and anal contraction can reduce the bulge in size and once less painful can be pressed back in as described above. Once the blood vessel is no longer sticking out where it shouldn't be, the discomfort of it is greatly reduced or minimized.
Depending on your specific anatomy and location of your other varicose veins, you can try the same technique to address those: adding firm gentle pressure to direct the blood out of the stretched part of the vein into the rest of the blood system.
DONT DO ANYTHING THAT MAKES IT HURT WORSE though! As in, don't 'force' the vein to shift or move, but take the time to relax and guide the blood out of the swollen portion of the vein.
For veins in the legs, other than the information from Adelle Davis' books on nutrition addressing the specifics of those and phlebitis, i haven't heard that 'pushing the vein' back in helps.
Here are a couple quotes from Adelle Davis' book, "Let's Have Healthy Children" that discusses supplements to help treat these issues - there's a ton more information in the book, of course.
"Several physicians have stressed that it is virtually impossible to have either varicose veins or phlebitis if 400 - 600 units of vitamin E are taken daily; and all who have studied this subject appear to agree that women should be given vitamin E as a supplement throughout every pregnancy." p 60
"[Hemorrhoids] have been produced in volunteers deficient in vitamin B6....I have recommended that several dozen persons having this painful abnormality take 25 milligrams of vitamin B6 at each meal for a few days. All except one have told me that their hemorrhoids completely disappeared. Once the condition is corrected, 10 milligrams of B6 at each meal have prevented a recurrence." pgs 49-50