Saturate a cotton ball with non-acetone nail polish remover.
Dab the stain repeatedly until most of the nail polish is absorbed into the cotton ball. Use a fresh cotton ball and more remover as needed.
Wipe the vinyl with a damp microfiber cloth to clean away any remaining nail polish remover. If you are cleaning the stain from a garment, apply a prewash stain remover and launder as usual.
Moisten the stain with several drops of warm water. Allow the water to penetrate the stain for several minutes.
Scrape away as much of the nail polish as possible with the edge of a spoon. Use a light touch to avoid scratching the vinyl's surface.
Saturate a paper towel with amyl acetate and blot the stain repeatedly. Repeat blotting until the stain begins to disappear. Use a new paper towel and more amyl acetate as needed.
Wipe the vinyl clean using a damp microfiber cloth. Apply a prewash stain remover and launder as usual if you are working with a garment.