If it is a surface scratch and not too deep, lightly sand around the area until you remove the scratch. Yu will probably remove some of the stain if it was used, so you will have to match that up and use the type of finish that was originally used.
Now if it is a type of polyurethane finish you might have a hard time blending in the new spot. Varnishes and lacquers are a little easier.
Try it on a similar piece of wood, even if you have to go to a wood supplier to match your color, it will definetly be worth your while.
