Bro, from what you are explaining, that sounds more like a Sebaceous Cyst ( Fat build up,deposit ), that can appear in any part of your body, you just happen to have it in your nipples/chest ...i actually had one on my right arm ( tricep) just like you are explaining, and visually it bothered me but it did not hurt , so i decided to have it removed, BUT my doctor told me, If i removed it, that ,most likely more will appear again,and it could be in different parts of the body... Well got it removed, several years later, more showed up, got a couple in my right arm now ( tricep and forarm) 3 in my legs, and one in my left elbow... ive seen different doctors, they all tell me the same story ( its sebaceous Cysts, and If i remove it most likely more will grow) this time im not removing them...Im also old now, so i care less ( visually ) :-)
If you think that Gyno bro, believe me, IF anyone, or even you, slapped your chest/nipple just a little, you would be in so much pain, that you would want to kill someone just for doing that...
read this
http://www.localhealth.com/article/sebaceous-cyst