A localized area of urticaria pigmentosa would be a possible differential diagnosis. Good prognosis and nothing to worry. Fixed drug eruptions could present similarly. Do consult your dermatologist.
Hello,
For such symptoms the possibility of granuloma annulare needs to be ruled out. It presents as a rash with reddish bumps arranged in a circle or ring. It presents as small, firm bumps (papules) over the backs of the forearms, hands, or feet. Treatment is necessary for cosmetic purposes and consists of steroids and intralesional steroid injections.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.