Bruises in different places will affect you in different ways.
Bruised head? Lower awareness. Headaches hurt.
Bruised shoulder, arm, hand? Slower weapon swinging, overall weaker.
Bruised torso/groin? Assume it's exercise fatigue, you're overall clumsier.
Bruised legs/feet? As mentioned later, no sprinting, slower walk pace. Jogging is fine.
How does this happen?
So, you're sprinting away from zombies, and run face-first into a wall. You fall over. Chance of a bruise in a random spot of the body, most likely head.
You jump from a window to escape zombies, and land hard from a height. High chance of bruising on leg(s) or hand(s).
Vault over a fence to escape zombies, and stumble a bit. Chance of bruises on ankle(s), or forearm(s).
Get into a scuffle with another player, and they kneecap you with an iron bar, baseball bat, crowbar, pretty much any blunt weapon. Depending on the attacker's weapon skill, chance of bruising in random part(s) of your body.
Sprinting and tripping over trees/zombies/pretty much everything that can trip you. Chance of bruise on ankles, hands, or face. Face bruising chance is increased should you fall on concrete, a wooden floor, or something of the like.
If you are wearing a bulletproof vest and get shot where the vest is protecting, there is a high chance the area will bruise, as a vest doesn't 100% stop a bullet, but it saves you from a lodged bullet or bleeding.
How do you treat this?
Ice. No bandage needed. Medicine bags have cold packs. Or equip something cold, that'd help Apply them to speed up recovery, although they aren't necessary. You can just wait them out, they aren't too bad an injury. Speaking of which;
How serious an injury is this?
It is not as serious as a scratch, but more serious than exercise fatigue. Think of it as the poor man's scratch. Not gonna kill you, unless it is on your legs. Even then, probably not.
