I've had this too.....
With me, I really wouldn't call it REAL painful....feels like it needs popped, so I inhale and hold, lift my arms about and behind and/or stick the chest out...
Sometimes it pops, most of the time it doesn't...when it does pop it hurts for a few hours then goes away....if it doesn't pop then that 'needs popped' feeling stays...
Another thing that I think works well is stretching...like on Pec day...I ALWAYS stretch the pecs well (before and during)....a PT showed me one in particular...you guys probably already do it, but if not.....stand at a rack/cage and put the bottom of both forearms above your waist on the front of the rack...(like a butterfly machine).....then just take one step in and stick your chest out (lunge like)....FEELS Great....switch feet and repeat.....Sometimes I get the pop, most times I don't....