What Causes Swelling, Redness And Brown Scab On Foreskin Of Penis?

Hi 5 days ago I thought I was having a genital herpes recurrence, I was having the telltale painful tingling in ny scrotum and buttocks. The next day my foreskin swelled right up and got extremely itchy and there was a blue Mark under the skin. I still presumed it was a herpes recurrence albeit a bad one. I went to the clinic to get some anti viral tablets but when the doctor examined me he said it wasn t herpes and that I d caught ny foreskin in my zip or I d been masturbating, which I d done neither. I haven t had sex for over two years. He gave me anti virals just in case and sent me home. 3 days later my foreskin is still swollen and red and the blue Mark has turned into a bigger disk Brown smooth scab that is cracking in places. I also have a swollen sore lymph node in my groin. What could this be? I m getting worried it could be cancer. Thanks Mark