Hello,
This bump can be due to boil, cyst or folliculitis. Keep the area clean and apply some topical antiseptics and warm compresses. Also wear loose-fitting cotton clothing and use an antibacterial soap or mild soap like dove.Avoid any kind of cosmetics. Topical antibiotics such as mupirocin or neomycin containing ointment are also useful.In case the symptoms persist then oral antibiotics and incision and drainage may be needed. Please consult a gynecologist in that case.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
It is most likely an ingrown hair that is still forming underneath the skin. If there is only 1 bump, i wouldn't be too worried about an STD.If your genital area, is itchy, sore or has an unusual smell then you should visit your gynecologist immediately .
Good Luck