I tried nail varnish remover (!) but it just made it worse. My couch is white and I live in a rented flat, so its really important I get it off!!
Usuanlly a non-acidtone nail remover will remove the spot without eating thru the fabric, but the trick is to blot it and not rub it. Considering that you have a white sofa though, and depending upon the type of fabric depends upon how it hold holds the stain. If it's on a seating cushion, and it still dosen't work your best bet is to flip it.
