to feel a pang of something
to experience a sudden, sharp feeling (often unpleasant) · a brief, intense emotional sensation
What's the situation?
Imagine you are scrolling through old photos and suddenly you see a picture from your childhood. You might 'feel a pang of nostalgia' for those simpler times. Or, if you accidentally forget a friend's birthday, you might 'feel a pang of guilt' when you remember! It's that quick, sharp emotional hit. 😭