That should be the head of your ulna. That is one of the bones of your forearm that goes from wrist to elbow. Is the bump on one arm different than the other in some way? Painful? Or were you just wondering what it was called? You also have several small bones in your wrists as well but they don't typically "stick out".
Are both of your wrists like that? If yes, and you did not injure it or having any pain associated with it, it is normal for the head of the ulna to stick out a little. My wrists are very boney looking.
Ok first of all, it is part of your ulna...it is part of the ball and socket joint that us people call our wrist...its completely normal...and second of all is everyone saying your are an EMT is a load of crap...if you passed highschool bio you would know that, let alone being an EMT