Small criticism

NIT

Think of what a fussy person might endlessly pick at, often something trivial or insignificant. It’s also a term for an insect’s egg.

Small criticism" hints at a minor complaint, and "nit" fits perfectly as an informal term for a petty or trivial objection. The word also plays on its literal meaning—a nit is the egg of a louse, something tiny and bothersome, reinforcing the idea of something small and annoying. It’s a concise answer that captures both the size and the critical tone of the clue.