Thanks for the query,
Groin area is prone to sweating,
This sweat attracts fungal growth.
You might have developed fungal infection
Treatment can be with oral antifungals as well as with topical antifungals.
You can apply an anti fungal powder like clotrimazole
This will keep the area dry and prevent infection.
Please meet a dermatologist
for exact diagnosis.
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.