Definition
To use excessive force or resources to solve a minor problem; to employ a disproportionately strong solution to a small issue.
He used the entire toolbox just to fix a tiny crack, it's like using a sledgehammer to crack a nut.
Deploying so many police officers to catch a child stealing an apple is really using a sledgehammer to crack a nut.
You just needed a needle, but you brought out a whole bunch of tools; that's using a sledgehammer to crack a nut.