When Pulling Back The Skin I Saw Little Stretch Mark

when pulling back the skin I saw little stretch mark like things which were painful as well. I decided to let it rest for a couple of days and see if it would heal by itself. When everything looked normal yesterday, I masturbated for the first time in a week and surely enough right after it my skin got a bit swollen and the pain with the stretch marks returned again. I also noticed that the skin is rather dry. What could be the cause of all this? And what can I do about it?