Hello, i have noted your concern,
The most common causes of painful lumps under your armpit are swollen lymph nodes. These nodes filter the lymph fluid and can swell up due to the following reasons:
A bacterial, fungal, or viral infection in the arm or breast, An infection in the entire body like
AIDS or herpes, Cancer, (usually breast cancer or lymphoma)
Lumps in the armpits can also form due to:
Allergic reactions
Benign fat tissue growths, known as lipomas and Cysts.
The most serious cause of these lumps is cancer. Hence, it is recommended to consult a specialist if they do not subside.
Next Steps
Please apply warm compression, hot water treatment like you need to Soak the towel in hot water and wring out the excess. Place this on the affected armpit for 10 to 15 minutes. Repeat the warm water treatment 2-3 times a day.
Also you can take over the counter pain medicine like paracetamol
Health Tips
If pain doesn’t reduce or get worsen please kindly consult
Do not wear tight clothes
Or apply any perfumes or deodorant which can irritate the skin and cause more pain to you