Do I have an STD, or a simple blemish?

Patient: Ok, I’ve had this single red bump on my pubic area. Been here about a week now, use to be fairly large, now is about dime sized. It had what appeared to be a white head so i put it off as a pimple. It kept getting bigger and was painful to touch, so I opted to pop it in the shower yesterday, perhaps not the best idea.It oozed out a lot of puss, but mostly blood. The bump is still there, with the white head being replaced by a black line. Although it is much smaller and does not hurt to touch anymore.I don’t think it is an std, but rather just a large pimple, ingrown hair, or maybe a cyst, but I have no idea.

Symptoms: Single bump.

Images:
Do I have an STD, or a simp...-1 Do I have an STD, or a simp...-1

Doctor: