Thanks for the query,
You might be suffering from a fungal infection
In this area it is called as Tinea cruris
It usually as itchy rash but soon gets infected and develops pain.
Treatment with anti fungals might be required
Please meet a dermatologist
for final diagnosis and treatment
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.