Nail polish is one of the most difficult stains to remove from upholstery, and is most likely to be successfully removed if the stain is fresh. The following advice is for cotton or manmade fabric. For silk, wool and other natural fibers, have the stain removed professionally.
The first step is to mix one tablespoon of liquid dish soap with two cups of cool water. Using a clean cloth, sponge the stain with detergent solution, blotting the stain until the liquid is fully absorbed.
Repeat these steps until stain is removed and then use a clean sponge with cool water to blot the stain. When complete blot the stain dry.
If the stain remains, it is best to contact a professional carpet cleaner to resolve the issue.