Hugs! Wishing you all the best with your treatment. I raise all my worries with my treating team (usually oncologist or gp) to get checked out just in case. Often there can be many reasons for soreness or swelling, but I have been getting it checked out each time for peace of mind. Recently I felt a tender lump under my arm but it went away by itself and ultrasound has confirmed there is no lump there. If it was cancer, though very scary, I would want to know asap so that action can be taken. Wishing you the best at this stressful time