Use a piece of bread to scrub the cheese grater; the bread's texture will grab the cheese without damaging the grater.
Cleaning a cheese grater with stuck-on cheese can be tricky. Water alone often isn't enough, and using a sponge can just push the cheese further into the holes. Here's how the bread method works:
Let the cheese grater sit out for a little while so the cheese hardens slightly. This makes it easier to dislodge.
Take a piece of stale or slightly dried-out bread. A crusty bread works best.
Hold the grater firmly and carefully rub the bread across the surface, using the bread like a sponge. The bread's texture will catch the cheese particles.
Repeat this process, using different parts of the bread, until most of the cheese is removed.
Rinse the grater with warm water to remove any remaining bread crumbs and cheese particles.
If necessary, use a brush with soft bristles to gently scrub any stubborn bits of cheese.
Dry the grater thoroughly to prevent rust.
To prevent cheese from sticking in the first place, spray your cheese grater with cooking spray before grating. The cheese will slide right off, making cleanup much easier.