It is probably a boil or ingrown hair. Wait a week and see if it has made it's way to the surface. Or if you are more like me and can't stand it, try to pop it. It will hurt really bad if you try now (since in is probably pretty deep if the skin isn't red). If you shave down there then this can cause it. Make sure to put lotion on after shaving to reduce irritation and in grown hairs.
If it doesn't get better (or pop) you will need to see a doctor so they can do it for you.
Good luck.