Hello. Welcome to hcm.
Lump and sore in that region could be mainly due to infection either related to chest wall or brest or lymph node infection
. If your age is more than 40yrs,cancer also has to be kept in mind.
I advice you to consult a surgeon who will take a xray first or ultrasound
if there is no pus outside. Then guided biopsy
of the pus can be sent for culture and you have to be started on antibiotics with or with out abscess drainage
If swelling is from lymph node,then pathological examination is to be done after fnac and treated accordingly.
All the best