I’m not a professional.
If you have a syringe and sterile needles I’d try aspiration fist after following all of
@casportpony ‘s prep steps just to see what kind of material is in there.
To aspirate, insert needle well into the lump, pull back on the syringe plunger to make sure you aren’t in a blood vessel ( if you were you’d immediately see blood coming into the hub (base) of the needle. If this happens STOP.
if it’s a muddled pink-tinged color I would consider that it’s safe to proceed.
Pull back slowly but firmly enough to get a sample and expel it onto a clean surface such as a white paper towel to example the color and texture of it.
*photo here would be good.
That might help you decide how to proceed.
If it’s thick, proceed but make the incision big enough the first time to avoid repeated pain and stress to the bird- to comfortably accommodate a syringe tip. I’d go for a 1/2 inch incision.
Flush copiously and massage. Whatever goes in, must come out.
Continue until you’re satisfied that this pocket is empty.
If flushing with diluted betadine or saline doesn't loosen it enough to dislodge it, you could attempt manual removal with tweezers boiled for five minutes then allowed to cool on a clean surface,
Or
with the end of a cotton swab with the cotton bud removed first. *so you don’t lose it inside the wound and compound your problems.