Not sure if have swollen lymph node armpit, but feels a bit large, sore. had allergy shot in same arm this week near armpit. will cause lymph to swell?

Needs evaluation : Hard to say what the cause is with out an exam. See your primary care doctor for this.

Armpit swelling: Depending on what allergy shot you got, prescribed by an allergist or at your primary care doctor? The allergen serum can cause local reactions on the skin and if large, may occasionally cause lymph node swelling in the armpit, although rare. It may not be related, it may be an infection somewhere else, see your doctor first.