When you say "on top", do you mean the bony bump on the outside? If so, that's called the Lateral Epicondyle....tennis elbow. I developed it from shooting a LOT of sporting clays. When I say a lot, I mean 1500 rounds a month. I ended up having two cortisone injections in the elbow with minimal results. I wore an elbow brace for about a year. In the long run you have to quit shooting long enough for the multitude of micro tears to heal....if they do. Sometimes surgery is required. Now, all that being said, NEVER go to the internet for medical, legal, or financial advice. Half of it's not right, some of it's very wrong, and some does more harm than good. See a doctor for this before it gets worse or not repairable. Good luck with it.