It seems like you have Tinea Cruris(ring worm infection
). I would advise to start applying Lamisil
Cream twice a day for 7-10 days.
If its also in the groin region the you can use Zeasorb powder to heal it up quickly and to reduce the friction which can do more injury
I am sure the rash will go away in 1-2 weeks time or may be earlier than that but you have to apply the cream for atleast 10 days.
These medications are available OTC.
Thanks very much and best of luck.