I'm 16 and circumsized. I have an almost complete ring of little bumps one by one just under my penis head. They're under the skin and just appeared recently. What are they?
Most likely you have pearly penile papules. These are small white (or slightly yellowish) bumps which appear on the edge of the glans (the corona). The distinguishing characteristic is that the bumps appear in neat rows. Click here for a picture of what it looks like (courtesy of Wikepedia). Studies have shown that anywhere from 8% to 48% of all men have them. They cause no known harm. A dermatologist can remove them with a carbon dioxide laser, but unless the bumps are large it is generally not done. The risk of the treatment is greater than leaving them alone.
The cause of pearly penile papules is unknown. It is not caused by an STD; virgins can have them. They appear most often in men between the ages of ten and thirty. They do tend to fade as you get older.