What can cause a bump on my vagina?

Bump: several things such as a sebaceous cyst, genital warts, skin tags, etc. Only way to know for sure what it is would be to see your physician or a gynecologist.

Many causes: A bump in the vagina can be of very limited consequence all the way to major problems. It may be a fibroma (benign), a wart (?), a simple cyst, an infection, a foreign body, a tumor, or other process. If concerned, get it checked out. You may just need reassurance but then again, you may have to have an excision, or biopsy or other treatment.