Chest popping

Recently I have been feeling pressure in my sternum (note, not heart or respiratory system, but in the bones and cartilage themselves). Thus when I pull my shoulders back and stretch to alleviate the problem, my sternum and the cartilage around it "pops"; is this a serious issue? 

No pain accompanies this action but it happens nonetheless. Is it damaging?

Help!

Eric

I am no expert by any means, but i dont think it is a problem my chest does that too from time to time. its just like popping your knuckles or any other joints. their is a technique that is used to do this for streching, and fish oil is good for joints it oils them up not the liquid thats just gross but the gel cap is the way to go.

My chest does this occasionally. I haven't noticed any pain or other problems associated with it.