may not be something that immediately requires medications. In the presence of significant sexual history however, an STD needs to be ruled out first. A solitary red spot may be a case of folliculitis or dermatitis. More likely it is a superficial skin infection.
Wash the area with a mild cleanser. Refrain from picking on the area. Wear loose underpants and try to keep the area clean and dry at all times. Observe the bump. If this enlarges and if redness or a discharge is present, then this may be something that requires medical attention.