Most likely it is Hidradenitis suppurativa a condition occurs when the hair follicles are blocked.Ideally you should consult with a dermatologist for further treatment.

Connect please

Possibly lack of hygiene or faulty technique during hair removal

Can help you, kindly consult and provide detailed history for proper diagnosis and further management

Need few more details Kindly consult

So its on and off umm... General surgeon might be necessary here, gotta examine a few things

According to your query and sign and symptom you want to know about the disease and cause and it's best Treatment of pain due bump underneath to left arm Please take consultation for better evaluation and best Treatment as it need complete history of patient as personal and family history. Please follow good life style as • take plenty of fluid and • take less spicy and fatty foods and • take home made food only and do exercise regularly with yoga and meditation and • keep positive attitude to fight any disease and any problem of your life .