My cousin and I were messing around and he punched me in the arm, it wasn't really hard but it wasn't soft either, anyway, two lumps appeared on my arm, they were about 1cm round and came out about 5-6mm then went down almost right away, it was odd so I had him try again and it happened again. It was on the muscle just below my shoulder and it kind of freaked me out, that's why I am asking if anyone knows what it could be here.