Good Morning..It is very difficult to come to a conclusive diagnosis on the basis of the information you have provided..Most likely it is either a fungal infection or seborrheic dermatitis which is skin rash frequently associated with dandruff..You should consult a nearby Dermatologist and take treatment for the same..Hope this helps..Warm regards
Next Steps
Consult a nearby dermatologist
Health Tips
Do not use over the counter creams and medicines