I've searched and searched and haven't been able to find an answer to this. It's also kind of hard to photograph but I here's what I could do. 
Anyways, I've had this ring here for at least a few months now. It doesn't really bother me, but it feels like something's in there, under the skin. Maybe a hair, curled around into a circle? Some kind of worm? Alien implant? What the heck? I know I know, I should just go see a doctor. Dermatologist? But I haven't yet, I dunno when I will, thought I'd see if anyone knows what it might be.
Oh, I could also mention, it’s maybe about 1/8th inch diameter. And it feels like a little tiny disk between my fingers. Pretty solid.
Just getting the location right: is this near the base of your penis? The most likely explanation is that it is an ingrown hair. These do occur quite often for most men. I would just keep an eye on it to ensure it does not develop out of all proportion …
It’s on the shaft, but not too far away from some other hair, so I imagine that’s probably what it is. All the images I could find of ingrown hair looked different and this one isn’t red at all, so I wasn’t sure.
It did turn out to be an ingrown hair. It eventually escaped it’s “ring” and started growing out in a line under the skin, causing issues, but also came close enough to the surface that I was able to remove it easily.