Hi krishna ,
Thanks for writing in.
It can be tinea cruris
or fungal infection
,erythrasma, ,flexural psoriasis
For correct diagnosis the images of the lesions and more info like duration,presence or absence of other lesions would be needed.
You can apply clotrimazole
cream over the affected area and take Tab zyrtec for itching.
Also oral antifungals and antibiotics may be needed for faster relief.
With images of the affected area and details of the symptoms a proper diagnosis can be made.
Images can be uploaded by the premium questions area.
I encourage you to visit a qualified dermatologist
for proper diagnosis and treatment.
Hope this helps.