What can I do about this misplaced ulna?!?

Hi, when I was about 5 I fractured both of my wrists. I got casts put on and they healed. I'm 15 now, and I think that my right ulna (arm bone) is out of its proper place! When I turn my wrists, it pops in and out of place (yes, the whole bone). I think that it somehow disconnected from my wrist during the healing process, and as I've grown its gotten worse. I don't know if this is a big problem or if there is an easy fix. My biggest fear is that the tension between the bones could somehow cause irregular cells to develop which could mean cancer. It is a real bother, so I was wondering if anyone knows about this. If so, I would like to know what kind of treatment there is, how much it would cost, and if it is a real threat to my health. Thanks a lot :D.