I completely understand your concern and I hope I am able to help you for the same.
You seem to have developed some form of an allergic skin rash
Avoid using any creams , oils or deodorants over the affected area.
Use a sunscreen when going out in the sun.
You need to apply a mild topical steroid
over the affected area twice a day.
Take oral antihistamines for itching.
Hope it helps
Best wishes for a speedy recovery
Dr Geetika Paul