I am a male in my 20s. Recently, I engaged in
mutual masturbation with a guy I met at a party. We alternated between stimulating ourselves and each other, and he rubbed the tip of my penis/urethra with his finger. He ejaculated on his chest and I did the same. Although we used lubrication, my penis was a bit sore afterward. While he said he is negative, I am not entirely sure, and now I'm worried about the possible risk from our encounter. How "safe" is mutual masturbation?