Rub the region with a raw walnut, working with the wood grain. Try passing over the spot many times until the marks vanish. Brush your fingertips over the affected region and leave it alone for a few moments. The oil in walnuts will be absorbed by the wood. If you then buff the spot with a clean cloth, the scrape should vanish. Walnuts are poisonous to pets, so be sure the room is spotless before bringing in any animals.