While playing a rugby match a few months ago (more or less 4-5 month ago) I got a knock to the check from tackling another player. At first I just thought I it was a bruise and would pass within a day or so. Yet my chest still has a pain when I stretch out my chest full with my arms backward, just right of the sternum bone. And sometimes when I'm in bed and I stretch. Pain is only caused by strecthing and certain type of movement, not by pressing on the area itself. No idea if its serious or if it will pass with more time.