What Causes Sharp Pain In Penis During Masturbation?

I am 18 years old and recently suffered what i think is a minor injury during masturbation. i felt a sharp pain (not too bad at all) in the right side of my penis, and with continuation it moved to the left side also. the pain has not gone away since (it was about 8 days ago) and i experience it in spurts, even when not erect. i am really worried