Hi. I Am A 300 Pound Male. Fell On My

Hi. I am a 300 pound male. Fell on my left side with my arm over my head. Most of the blow went to my left man boob. I can left my arm over my head. I can breath normally. But my peck is killing me. It is twice the size is lower than my right peck. it hurts under my arm, on the bottom of the peck and the inside by my sternum. What has happened? What can and should I do or be concerned about? Treatment?