Sorry, I just have to blow the "unnecessary panic" whistle. C'mon, burgundy, there are plenty of bony, weird masses in our chests, and from what you're describing, it certainly sound like your sternum. STOP feeling around for your bones, or your friend's bones, and then sit there and compare/contrast what they feel like. You have NO IDEA what those things are "supposed" to feel like in the "normal" body. You're fine. Stop manufacturing things to worry about.