I have gone through the detailed history and description provided.
I can think of two possibilities in your case a fungal infection
or an eczematous rash
. As the lesions are tender swollen red it seems a superadded bacterial infection is present . In such cases firstly the superadded infection needs to be treated followed by treatment of primary cause.
I would advise that you consult a dermatologist
nearby. Bacterial infection would require oral and/or topical antibiotics. Once the infection will clear off antifungal or steroid
cream may be prescribed for athlete's foot or eczema accordingly.
Hope that helped.