hello Im a 27 yr old male.A few days ago i was riding my bike which i havent rode in like a year or longer and when i woke the next day i felt a  bump or maybe popped vein in my arm pit that is real sensitive and painful when touched..it is noticeable when i raise my arm and roundish in shape. Please let me know if this can heal itself naturally or if i need to see a doctor.Thank you.
Welcome to Chat Doctor. 1. The symptoms and features of the lesion / lump suggest hair follicle infection.2. Other possible cause could be abscessed / infected cyst.3. You may need to get an ultrasound to assess the nature of the lesion, its source and extension (to rule out the vascular cause as you said)4. Treatment generally a course of antibiotic will be enough.5. In bigger lesion not reacting for antibiotic, a small incision and Chat Doctor. 6. It will be good if you can get a GP appointment and do needful tests and treatment done. Good luck. Hope I have answered your query.Anything to ask do not hesitate. Thank you.