do somebody/yourself a mischief
do (oneself) a mischief
To do something that harms oneself. Primarily heard in UK, Australia. I think you'll do yourself a mischief if you try that risky skateboard trick.
do (someone) a mischief
To do something that harms someone else. Primarily heard in UK, Australia. You sure did your brother a mischief by including him in that dangerous game.
do yourself a mischiefINFORMAL
If you do yourself a mischief, you injure part of your body. I think I'd do myself a mischief if I tried to copy any of her dance moves.