Hi, My name isXXXXX you for using Just Answer. I am happy to help you with your concern.
You have probably developed a fungal infection or a yeast infection. You can try treating this yourself but if the symptoms do not get better or get worse you will need to see a dermatologist to get a prescription strength cream or an oral medication. They will probably scrape your skin and look at it under a microscope to determine exactly what type of infection it is.
Wash the area with an antibacterial soap and then pat dry the are very well, apply a fungus medication (look for ones for athletes foot) Wear cotton underwear and loose fitting pants. Try this for 2 weeks but if it doesn't get better go ahead and see a doctor.
I hope this has helped. Good luck and if you have any further questions please let me know. Have a good day.