Collarbone trouble?

OK when doing bench, no matter if its flat, incline or decline, at full extention I get a bad pain in my collar bone in a spot I broke it when I was in 6th grade (I'm now 27 years old). Is it possible that its the actual bone hurting or is it just a muscle there? How much do I loose if I only go up about 3/4 of the way on all bench exercises? Anyone else have this problem and find a fix? It might just be an odd thing as it just started this workout but want to get a head start if I need to check/change some things...

Thanks