Please look at this need help!?

This is kind of hard to explain but I was laying down and I felt a little nervousness coming on. I have occasional anxiety attacks and as I was doing some deep breathing I could feel something almost popping on my right side under my sternum at the end of my ribs kind of near my stomach but more to the right. And then I felt it and I could push it in a little and it was like it was attached to the end of my ribs and it would pop back out. Almost like cartilage feeling and it was down my ribs not sure how far but only on the end. I dont feel it there anymore and it kind of hurts there not really sharp pains but more of a dull pain. Any ideas on what that was?