Hi, I am doing masturbation regularly. And my penis seems healthy and had no problems at all. However, just a few days back i masturbated very rigorously without any friction. And at that time, i noticed little blood on my fingers and then i saw a little scratch on penis shaft skin nothing much i just washed the penis and went asleep. Now , 2 days back i just noticed a black dark colored patch at the end of my penis shaft where the skin rolls...it does not hurt at all. And even not swelled. Its look link a dark blackish purple ink spread on penis shaft. I am worried a lot about it. As i have read something about penile cancer also. So i am so worried what to do about it and how should i make it go. It really looks black big mark. I don t know what is the exact reason for it but i am sure it is not a birth mark. So please help me here as i am totally freaked out after reading those penile cancer posts online. Thqnks, Vibhu