a flea in (one's) ear
A sharp, strident, or disconcerting reproof or rebuff. She gave me a flea in my ear over my spending habits. I'll be sure to put a flea in his ear the next time I see him!
flea in one's ear, a
An annoying hint or a stinging rebuke, as in He has a flea in his ear about their relationship, or If he doesn't bring the right equipment, I'll put a flea in his ear. This expression originated in French and has been used in English since the 1400s.