5 days ago i noticed a very small bump on the head of my penis, on the top, near the tip. It is very small, the size of the head of a pin, and is slightly lighter colored than the rest of the skin. It has no sensation (no burning, no itching, no pain). It's more noticeable some time than others (sometime whiter, sometimes flesh colored). It's more visible when I'm erect and when I tighten the skin around it.
My last unprotected encoutner was in 5 months ago. Could this single bump be an STD? Like HPV or Herpes? If not, what could it be?