Had that when I was doing too many pushups with insufficient breast muscles to support. Nothing serious, but it can take a decent time to heal completely. See a doctor to get proper advice. Most likely though just try to avoid strain on the injury and don't power through insane reps, before you have built the support structure, after it's healed.
This brings up something I was thinking of earlier. If you Google symptoms for something you'll have a plethora of things to choose from. I often wonder if doctors themselves know, and just because they hold the title of being one is that the reason we listen to them? Think about it, look at how easy it is for them to prescribe you with things that you probably don't even need which leads to more problems.
I'm not saying to not believe in doctors but at times you have to be careful in doing so. I was once given antibiotics for a common cold when all I really wanted was some cough syrup, he kept insisting I had pneumonia. It almost hospitalized me cause it made it worse. Since then I only go for checkups.