lymph nodes in your arm pits ( axillary) can be due to a virus in your system or even cysts. If they last more than 2 weeks, i'd have them checked out. Yes they can be very painful and swollen. you can try ice or heat if it helps, but also alevee or naproxyn ( antimflamatory med) to help bring the swelling down. . not tylenol products they wouldn't do that. some auto immune like sjogerns causes this..
You should see a doctor if you have swollen lymph nodes.