From the description it seems you could be having fungal infection
of groins. For the same a course of oral antifungal
like fluconazole is required along with topical antifungal
creams like clotrimazole
. If the lesions are too itchy, you may also take oral cetirizine. Wear loose cotton clothes, keep the area dry and well ventilated.
Hope that answers your query. Take care.