First, I would go and talk with one or both of your parents, or another adult that you feel comfortable talking to.
Yes, it's possible for a teen to develope breast cancer, but it's pretty rare. If you have it in your family then it raises your chances.
I'm not sure about your situation, but I would definatly get it checked out just to be safe. It could be cancer, something else or nothing at all. But you really should have a Dr. check it out.
If you don't feel comfortable talking with an adult, then you can make an appointment with a Dr. and have a friend take you or go by yourself.
Good luck and I hope everything turns out ok!
both of my nipples are inverted, have been since puberty. i also know of a girlfriend that just one of hers is. it might just be that, an inverted nipple, so hop in a cold shower and see if anything changes!