Hello, Lumps under the armpits can be due to irritation from shaving, rash, lipoma, inflamed hair follicles, trauma, boils, carbuncles, cysts, folliculitis, ingrown hairs, etc. Serious medical conditions that like lymphoma, leukemia, fibroadenoma, soft tissue sarcoma, breast cancer, etc. You are suggested to get clinically examined by a GP, get routine blood works, CBC, urinalysis, imaging tests, histopathological examination and biopsy if needed be done so that the cause can be detected and treatment started at the earliest. You will be given a combination of conservative treatment with drainage, aspiration or surgery if needed. Numbing and tingling is because the nerve is being affected due to the lump. You have scabs behind the skull, use medicated shampoos to reduce irritation due to dry scalp, scalp psoriasis and dandruff. You can also use natural remedies like colloidal oatmeal, tea tree oils, and apple cider vinegar to get rid of it. Get clinically examined by a dermatologist to treat the underlying cause that is causing the scalp scabs or sores and prescribe treatments accordingly. You are also feeling crawling of worms around the anus. Get dewormed. Always wash hands before eating and maintain good hygiene. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician