There were a lot of good things said in the other answers, and all I would add is that when I get a pain in my chest, alot of times, for me, it's gas bubbles stuck in there. I'm not sure whether it's in the muscle tissue, or something else, but often it is located right below or right underneath my boobs and I can actually go up to it with my fingers and pop it. No kidding! And if that's what it is, I will know immediately, because then, the pain is gone.
If the pain still exists, then do see a doctor. It could be a heart condition especially if the collar bone area is also soar like you've been running. (Don't spend too much time trying to do what I said I do, I would see doctor first just to eliminate all other possibilities, and if all else fails, do what I said.) It sounds wierd, but if it's trapped gas, it works.
Good luck and get well,