Clay bar. You can buy clay bar kits at most stores that sell car supplies. Follow the directions on the box.
I work near a place that does a lot of outside spray painting. I sometimes forget to put my car cover on, and my car gets completely covered in little specks of over spray. The clay bar removes industrial spray paint (they're painting boats) so I can't see why it would take off nail polish.
DO NOT use anything like paint thinner, nail polish remover, or any chemical based paint remover or cleaner. These will etch through the clear coat and ruin your paint.
If it's a new car paint thinner or wax grease and tar remover, make cloth damp with it and light rub till gone, polish area. All at Repco, supercheap ect
Your paint is probably already ruined . Nail polish remover is basically acetone which will damage your paint .
If your car was kept well waxed the nail polish may chip or peel off if you're lucky .
WD40 works well , the sooner the better...
My kid have put nail polish on the passengers door and I don't want to damage the paint job..please help..