weird spot on base of penis

Hi there I am writing to you because I had a spot on penis too. I was eighteen years old back than and I was sexually active, but I had sex just with my girlfriend and our sex was protected every time. According to that I decided to visit  a dermatologist, who  gave e some creme that neutralize my problem. If we talk about you I need to know have you ever been sexually active and was your sex protected if you ever had sex? Finally it can be due to puberty or if you are older you should see a doctor.