Hello doctor. I am 16 and am not sexually active, although I do masturbate about once every day or so. About a year or two ago, a pimple like bump appeared on my penis, on the underside about an inch below the head and on the left side. At first, the pimple disappeared after a week or so, but it has continually returned every few months. Usually it was a pinkish or purplish color, and resembled a pimple so I didn't worry. Two weeks ago, it returned as a pimple and soon left. However, two nights ago it returned as a mostly purple pimple except with a black head, all of which is beneath the skin of my penis. I am pretty concerned and could really use your opinion.
Thank you