the most likely infection is a fungal skin infection
. the best way to treat that would be to use an anti fungal cream such as miconazol which is available over the counter, and using some hydrocortisone cream
to help with the itching. make sure you wash the area with a gentle soap first to keep it clean. it is also a good idea to wear loose fitting underwear so that air can get to the area and keep it dry.
if that doesn't help, have your doctor check it out to make sure it isn't something else. I hope this helps you, please let me know if you have any more questions.