Meaning of “smart” - Learner’s Dictionary

smart

verb [ I ] uk us /smɑːt/
UPSET

to feel upset because someone has said or done something unpleasant to you:

The team are still smarting from last week's defeat.
PAIN

If part of your body smarts, it hurts with a sharp, burning pain:

The smoke from the fire made her eyes smart.

(Definition of “smart verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)