Your SON took his hand and smacked the clerk's son, harming him.
harm or injury - usually financial harm or financial damage: 機嫌を損なう（きげんをそこなう）
a disadvantage or handicap
damage - to your body, but also to your property. Often used when you lose money on a deal. Usually implies that the damage was not intentionally caused.
損害 傷める 被害 損なう