The views expressed by me are for educational purposes only and do not establish a doctor patient relationship.
I am Mysticdoc, experienced Internal Medicine Specialist.
I am here to help you with your concerns.
Since this is a painful lump, this can be an infected lymph node under axilla.
An infected lump can cause chest pain as well due to the inflammation.
Given her age, the risk o cancer is very low.
So although this is not serious condition, clinical evaluation is still required.
A course of antibiotic will take care of the issue.