The other day I noticed that I had a red bump on my right lip to my vagina. It is all the way to the back toward my butt, but is on the outside of my vagina. When I leave it alone it doesn't really bother me but sometimes it gets irritated rubbing in my underwear. It doesn't hurt or anything unless you touch it, it is a little tender. I tried to look up what it could be online and couldn't find anything. I only sleep with my fiancé, so I don't think it is an STD. What could it be?