Important question about masturbating and penises?

I am 16 and been masturbating for a long time. Today i was masturbating in the shower and after i was done and was changing in my room, i noticed some slight reddish marks on a part of my penis. (They didn't hurt at all.) I have not had that in a long time and they would always heal after. I heard they were called tiger stripes and are from masturbating too hard sometimes. I just wanted to know if this was normal? Also, Is this serious or not? Thanks!:)