Seeing as your floor has just been refinished, my first call would be to the person who did the refinishing. I wouldn't be suprised if they stepped in and helped you out gratis...though it depends on the severity of the scratch.
With poly finishes, it's often near impossible to blend a repair with old work. since you have "new" work, it's a little easier.
the best way to get an invisible fix? It does require a bit of work:
Mask off the perimeter of ALL of the boards that were scratched. Run your masking along the board edges, and at the butt joints. You want EVERY bit of EACH board that was scratched inside the perimeter of your masking. All boards should in one fully contained area...in other words, mask off the damaged boards as a whole, not individually. I hope that makes sense.
Sand down the boards to bare wood.
Repair any damage to the wood fibers.
Stain as/if required.
Re-seal, using the same poly and application techniques that were used by your refinisher.
Remove the masking.
It is a bit laborious, but it's the only way I know of to get a truly invisible repair to a damaged floor that has a poly finish.