A scratch in a piece of furniture is usually impossible to eliminate completely without refinishing the piece. However, you can often hide it pretty well with any of a variety of stain pens or coloured wax crayons. They can simply be rubbed in, or melted, even colours mixed during melting and flowed in. This does not give a resistant surface, and no finish will stick to it, but it does hide a scratch.
The products shown on this segment were picked up at ordinary paint departments of renovation centres -- plus a few kids crayons.
For more detailed information on repairing and/or hiding scratches, see my article on Eleminating scratches from furniture.