expression
rubbing salt in the wound
Idiomatic expression used when someone makes a painful situation even worse, often by reminding the person of their failure or misfortune.
失恋したばかりの友達に、元カノの結婚話をするなんて傷口に塩だよ。
Telling a friend who just had a breakup about his ex-girlfriend's marriage is like rubbing salt in the wound.