Unusual spot? What could it be?

Patient: Hi, I am curious about a spot that has appeared on the base of my penis. It has been there for a few months now. Not painful, not broken or hard. It’s a circle, deep brown in color, with a flesh colored bit in the center- almost donut shaped. It seems totally innocuous but it has really been bothering me- mentally. It doesn’t seem to match right up with any std I have researched. What could this possibly be?

Symptoms: None