A month ago I had a one night stand with a girl, we did not have sex but there was rubbing of the genitals involved. The next day I felt a tingling on the end of my penis which continued for about a week so I went to the local GUM clinic and got tested, all the results came back negative. A week later I noticed a single sore on my scrotum, I went back to the GUM and they said it did not look like herpes. I have had the sore for 2 weeks now and it has not changed in any way however this morning I developed a slight itchy rash on the tip of my penis. Does anyone have any ideas as to what this could be?