Lump in my armpit i think it's lymph node movable,about 1.5 cm painless i noticed it four days ago when should i see doc? no other symptoms

Lymph node: Could be a lymph node that is just reactive. But don't know the reason. If you have any fever, chills, cough, loss of weight or any other concerning symptoms, you need to see a physician. If it persists or enlarges you need to see a physician. If there are overlying skin changes, you need to see a physician. Tests may include trial of abx, cbc c diff, ultrasound/MRI, or referral to surgeon.