When I was twelve, after being in a public swimming pool I had a very sharp extreme pain in my penis just below the glans, when I woke up the next morning the pain was gone but there was an oval dark area of pigmentation in that area. over the years this dark patch has expanded and now encircles the shaft of the penis where normally a circumcision scar would be. I tend to doubt it is just a scar since it appeared suddenly when I was 12. Occasionally I get sharp pain there but usually there is no pain or symptoms, but blood flow is restricted below this band of discoloration during an erection--it takes a while for blood to move to the tip, like this band is constricting blood flow.