Thanks for your query,based on the facts that you have posted it appears that you have developed granuloma
in the region of your groin due to scratching and secondary infection.
You need to take broad spectrum antibiotics like Cefotaxime
along with anti inflammatory medication like Diclofenac
twice daily ,
Ensure to clean and wash the area with warm water twice daily,
Once the infection subsides you may need to get it excised under local anaesthesia by a qualified General Surgeon