I'm a 15 year old boy and my right nipple hurts sometimes. There's this reddish mark on the side of the middle. I guess it's a small scab. I have pain when my t shirt rubs against it. Here are some details about me that I took into consideration. -I lost about thirty pounds in my first year of high school from my PE class and making smarter food choices. -I recently started Summer school PE so I can have a 2nd elective next year. In SumPE, we do around 3 to 4 hours of exercise causing me to sweat a lot. My pain, from what I can remember started a few days ago. My guess here is that the sweat from SumPE is causing irritation on my nipple leaving a red mark. I've read other things on here about boys squeezing theirs and pus coming out so I don't want to try it. But if I do, and it comes out, should I see a doctor? Should I try at all? Do you have any idea what this could be? Was i right about the sweat? I feel pretty confident with that one. Please answer soon. I hate this feeling of thinking about what it could be and not knowing what it is.