Bruises and a bloody nose and black eyes are not injuries...They go away and leave no impaired anything after a few days.
Also obviously when I was counselling that mother to smack her kid as he attacked his brother, "so as not to cause any kind of physical damage" is implied.
You are off base. I can leave my front door right now and smack 40 people, and in 3 days, there will not be evidence that it ever happened except in their minds.
"Ah, those endless forests, and their horror-haunted gloom! For what eternities have I wandered through them, a timid, hunted creature, starting at the least sound, frightened of my own shadow, keyed-up, ever alert and vigilant, ready on the instant to dash away in mad flight for my life. For I was the prey of all manner of fierce life that dwelt in the forest, and it was in ecstasies of fear that I fled before the hunting monsters."
Jack london, "Before Adam"