Hi.  In my childhood I was once involved in anal sex with other child who was elder than me. I am sure it was not penetrative like adults do but kind of like only upper kind of thing but i am concerned whether that can transmit any STD to me as the boy with whom i did was elder and he might had learned that because someone had anal sex with him or he might had seen that kind of thing. Im concerned cause ive got grain type of thing beneath my scrotum and very small grain like things on my penis which are visible if look carefully. I consulted dermatologist in the past as they appear and go after treatment but comes back after one or two years. What should i do. Please help