Sore armpits may be caused by local soft tissue injury, lymphadenitis, or diseases of neighboring organs.
1. Local soft tissue injury: local stimulation by external forces or excessive exercise, resulting in muscle ligament strains, soft tissue contusions, etc., will lead to the symptoms of underarm soreness.
2. Lymphadenitis: axillary lymphadenitis can cause lymph node congestion, enlargement, pain, etc., which may cause a little bit of underarm soreness.
3. Diseases of neighboring organs: for example, mastitis, breast hyperplasia, breast tumors, thyroid diseases, etc., may lead to swollen lymph nodes in the armpit, which may also lead to a little bit of soreness in the armpit.
There may be other reasons why your armpits are a bit sore, so you need to go to a regular hospital for a checkup to clarify the cause.