Do yourself a mischief
Definition 1 of 1
Pro Tip 1/3Colloquial Usage
Used in informal situations among friends or family, not in formal or professional contexts. 
Watch out playing football on that rough ground, or you'll do yourself a mischief!
Pro Tip 2/3British Expression
It's a British phrase, so it's recognized and understood mainly by British English speakers. 
I told him not to carry all those books at once as he might do himself a mischief.
Pro Tip 3/3Minor Injury
The phrase implies a light or minor injury, not a serious one. 
Don't run too fast on the icy pavement, or you'll do yourself a mischief.