Strange symptom on penis head, what should I do?(pic)

It started about 2 weeks ago. i had a red bump appear on my penis immediately after having unprotected oral sex. The bump looked like it was filled with blood like a hematoma and i thought it was just bruising as i was very tender afterwards. About 2 days later the bump had gone down and left a red spot. it seemed to have burst but there was no bleeding. and it didn't hurt so i left it there and waited for the red spot to disappear. its been 2 weeks now and the red spot is still there. Could it be a possible STD? even though it appeared less than an hour after sex?

image

can anyone out there help?

sorry, but idk what is that too. but for your peace of mind. book an appointment for the doctors opinion. and take care your proper hygiene too.