How do I fix a spot on my wood desk?
Tinted shellac: adding a metalic dye to a dewaxed shellac: Advantage, can be done in layers, fast drying.  Finish can be blended and buffed.  Once blended, an appropriate top coat to protect all.
Stain or dye directly to the 'noticeable spot'.  Over-finish with spray can of clear coat : Lacquer, shellac or polyurethane as appropriate.
Stain markers (like a kids paint marker) are available in a multitude of wood tones.  They can be blended on surface and removed with paint thinner as needed.  They should be fixed with an over-finish as in step 2.