Hello,
The single pimple sounds like infected hair follicle or a sebaceous cyst. It is a closed sac occurring just under the skin which contains a "pasty" or "cheesy" looking substance called keratin.They may occur anywhere on body but scalp, ears, back, face, and upper arm, are common sites for sebaceous cysts. If they are painful means that they are infected and hence surgical excision may be required.
If it grows or becomes warty, then the possibility of seborrheic keratosis or wart has to be ruled out.
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.
no i have not been sexually active it just randomly appeard ... but thanks for the help!
I have a brother who had a similar experience. One its most likely an ingrown hair. If it is clean the area and remove the hair with a tweezers, clean with hydrogen peroxide. Avoid shaving in opposite direction of hair growth. Two, have you been sexually active without protection before the bump arrived? Did the bump ulcerate? is it still there or did it go away? Dont freak out the likely hood of cancer is very close to non, especially if its not a white patchy area on the shaft of penis..