Thanks for writing to us.
The child might be having an eczematous patch( most common being atopic eczema
). It responds to emollients and steroid cream like hydrocortisone cream
Another less common possibility could be fungal infection
Please consult a dermatologist
nearby for diagnosis and management. YOu may also use the premium services of this website to upload image of concerned area for diagnosis and treatment.
Hope that helped.