Suggest Treatment For Red Spot On Chin

I have a red spot on my chin that comes and goes. Looks just like a bruise. No swelling, tenderness, itching, etc. Almost looks like purpura, but its just the one small area and it it intermittent. It will appear every few months, remain for several days then spontaneously resolve. I ve tried to have it looked at by my doctor but by the time I get in for an appointment it s gone (and doesn t seem serious enough for urgent care). No correlation to meds, food, heat/cold, menstruation or anything else I can think of - just seems to randomly appear then resolve. Any ideas?