It is not uncommon, especially if you live in a climate that is warm at this time of year, to develop a fungal infection. Visiting a doctor is best, but if you can't at the moment, over-the-counter anti-fungal creams can get rid of fungal infections. There are several with different active ingredients, so unfortunately, it can be a game of trial-and-error to find the one that cures the specific infection you may have.
Make sure you keep the area as dry as possible - pat, but do not rub, the area dry after showering, and allow as much additional time for air-drying as possible. The more moist/humid it is in that area, the harder it is to get rid of.