Thanks for posting your query at DoctorSpring.com. First of all, my apologies for the exceptional delay with the reply.
You seem to be having nummular dermatitis. It's an eczema. You need to treat it with application of higher strength steroid cream like mometasone which requires a prescription.
The cortisone cream that you are applying is a mild cream and hence may not be effective in treating it well.
It's a treatable condition and needs proper treatment.
Hope this helps, Please feel free to ask any follow-up queries.