I have a 6yr old daughter with little to none allergies. Very healthy and a bit clumsy.

She came to me two days ago and said her back was hurting. On the base of her spine there is a large spot. About the size of a quarter, yellowish inside, scabby dark middle ring, and outer ring, rashy red. What could this be? There are no indications that it is a bite, and it isn't leaking anything. If anyone can help? Short of bringing her to the clinic.......