I had a cystoscopy a couple of days ago, and the pain subsided yesterday. This afternoon I masturbated, and it didn't feel like I was overly rough...although I was careful not to squeeze my penis, and primarily jerked the skin. In the shower, the skin was very itchy, and now the skin near the head of my penis is all swollen. It's dry, there's no discharge or pain...just swelling. Should I be worried about this, and what causes this?