Toothpaste is not only good for brushing your teeth, but also good for many other stuff. This example shows you how to use toothbrush to remove nail polish stain.
Remove nail polish as much as you can with nail polish remover. If there is stain, apply toothpaste on the stain, and scrub it with your fingers, nail brush, cotton tips, or paper towel. Lastly rinse off the toothpaste with warm water. Repeat the process if needed.