There's a couple of machines I use that sorta bruises my sternum/rib area. On of them being a Hammer Strength back machine that when I am sitting in it with the brace pad against my chest and the heavy weight piled on, it really puts pressure there during the set and I am feeling it for a few days. Almost like a little ache and somewhat sore to the touch
I've been told I have this too....(but what the f--- do military doctors know).....been out seven years and no more pain.....it does suck when you can't pop you breastbone though
Putting your elbows back and sticking out your chest will often yield a pop from your sternum. The pain you speak of may very well come from bouncing the bar off your chest when bench pressing. I know that's what I traced mine to.
Yes, I've had it before. It is tendonitis bursitis where you stretch the ligament too much and it becomes inflamed, imo. The pain for me was just inside where the front deltoid meets the chest/cavicle (if that makes sense lol). Now...you can still train a long time with this injury with the pain varying from time to time.
Finally, with me anyway, it just felt like I was tearing the muscle. I took 2 1/2 weeks off all benches and about 1 month off military press. The first few workouts back I eased into only doing flat bench on chest days and then after 1 full month started doing only seated dumbbell military press. It worked and I healed up. I think Muscular Development had an article in the injury section about 2-3 months ago with a diagram. Good luck!