Hi, I think I pulled a muscle in my left arm and under my armpit a week ago, they were sore but getting better but this evening, my left nipple began paining me, if feels tender and sore and possibly a tiny bit inflamed. I don't know if there is any correlation with the pulled muscles. What could this be? Thanks

If you call up a picture on Google of the musclature in your upper body, you will see how the muscles are connected. You will then realize why your breast is tender, and no, it can't be inflamed from this. It is all related to a muscle pull.