My son has a small circular rash on his arm, size of a quarter, started yesterday, raised like hives today? we just put some anti fungal cream on it but he says it burns a little

This : This is difficult to answer without a clinical examination. It could be many things including eczema, hives, fungal infection, or other possibilities. Take a look at the picture of ringworm and hives on the link below to see if it might look similar. I would then see a dermatologist for diagnosis and treatment options. I hope that helps!