What is this circular thing the size of a small pea on the left side of my rib cage kind of attached to the sternum? It is not really seen, I can only feel it when I try to press on my skin, so it is more internal. It doesn't hurt as well. I have been experiencing shortness of breath for the past two weeks or so, and I am coughing some right now too. And a phlegm issue that has been going on since forever.