Dave, DMD, Adam - all correct.
DD you're a fool, bone is a bone is a bone so can be broken many times.

newbie - some people have a tendancy towards this the same as getting a nosebleed or getting cut. The best advice would be try not to get hit so much! It can be a worry but think of it like an identify feature of certain boxers besides when you're rich and famous and retired from fighting you can get it fixed