I have athletes foot and burning sensation under my scrotum?

Tolnaftate: A tolnaftate cream is still probably best for most athlete's foot, a diagnosis a lay person can make easily. I'd apply it to the sensitive area on your bottom as well and see what happens. Keep these places dry especially after you exercise. If you don't get a good result in a week, physician's office visit is in order.

Jock itch: It is certainly possible that you have a fungal infection in both locations. Antifungal creams are a good start. Try and look in a mirror and make sure you have no open wounds under your scrotum prior to applying any medication. If you don't and there is just scaly skin or redness you can try the antifungal cream and if no improvement see your doctor.