I’ve had a look at the picture, as well as had a dermatologist friend look at it. You should visit a doctor/dermatologist to have a skin scrape test (looking for fungus) and to find out a bit more history about the rash. It looks a bit scaly, so a fungus infection has to be ruled out. If it’s a fungal infection, it can be easily treated. Obviously, it could also be due to other common conditions, such as eczema and psoriasis, especially if it runs in your family or you had childhood eczema. It’s unfortunately a little difficult to tell as the photo is too close up.