hello. Welcome to HCM
The common causes for stinging, itching and more over pain in the arm pit is usually infection of hair follicles and sweat and apocrine glands which are abundant in the area. They are usually very very painful due to many nerve
endings present in the area. the best approach is to use broad spectrum antibiotics, analgesics and antipyeretics as required and take local care. In local care, you need to avoid use of alcohol containing deodorants, and keep as much dry as possible by application of medicated talcums...(e.g neosporin
However, if the pain is accompanied by redness
and marked swelling, it can be indicative of lymph
node involvemnt. In this case, a debridement by a good surgeon will help.