Welcome to Healthcare Magic.
Your skin condition is most likely seborroeic dermatitis or it might be a Fungal infection
or erythrasma or others.
I like to suggest you the following....
1. Wash this area with a shampoo containing Ketoconazole
2% e.g. NIZORAL SHAMPOO. regularly for 1 week then 2/3 times in a week.(keep it on affected site for 15 minuetes.
2. Take Cap. Itraconazole
100mg Twice daily for 1 week
3. Apply an antifungal plus steroid cream e.g. BETNOVATE CL cream twice daily for 2 weeks.
Consult a dermatologist
2 weeks later.
Dr. MM Mahmud,Dhaka, Bangladesh,(email@example.com)