Blot the nail polish with paper towels immediately, if the spill is fresh. Do not rub. Once the polish has soaked into one paper towel, replace it with a fresh one, repeating until as much of the polish has been removed as possible. Wipe any remaining nail polish with an isopropyl alcohol-moistened cotton pad.
Scrape dried-on nail polish from the surface gently, using a plastic putty knife. Be careful, as the dried-on nail polish may take the wood finish with it; if the polish won't budge, don't force it. If you're able to scrape the polish away, wipe the area with isopropyl alcohol.
Remove a tough nail polish stain by spot treating it with non-acetone nail polish remover. Soak the tip of a cotton swab with remover and rub it on the nail polish, avoiding contact with the wood. Blot the dissolved polish away with a a paper towel as you go, until the polish has been removed. When you've almost reached the wood finish, switch from the remover to isopropyl alcohol.
Clean the remaining nail polish residue with oil soap and a damp sponge. Allow the spot to dry.
Spot-repair the finish, if necessary. Lightly sand the spot and wipe with a moist cloth. When the spot is dry, apply wood lacquer with a cotton swab. Allow the spot to dry overnight.