G.J.
You didn't say where the nail polish was. Is it on the skirt? The bodice? How big is/are the spot(s)? If it will lend itself to it, there are many cute appliques that you can buy and just iron on. If you are very "crafty" you can buy some tulip paints at a craft store that sort of match the polish and add "accents".
One thing I would do tho - when the dress has been outgrown, save it and use the nail polish squares in a memory quilt.
GJKBEAR