If the scratch isn't too deep,or into the wood as stated above, then you can fill it up with finish. It's a slow process but can work if you're patient and careful. Pick a finish that builds well, dries fairly fast and finishes out glossy like tru-oil. Take a toothpick or wood q-tip stick and sharpen it to a point with a knife. Dip the point of the stick in the finish and apply it into the scratch. Build it up slowly until it reaches the surface, letting each application thoroughly dry, and then blend it in with a rubbing compound.
Hope this helps.
