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 yourself a mischief
INFORMALIf 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.
ˌdo somebody/yourself a ˈmischief
(British English, informal or humorous) hurt somebody/yourself: You could do yourself a mischief wearing such tight trousers!