Sweep up any loose dust or debris from the discolored area of your hardwood floor.
Buff the floor gently with a piece of steel wool if it has a varnish or urethane finish. This can remove some of the discoloration.
Clean the area thoroughly using a wood floor cleaner. The floor cleaner will remove oil and wax finish. Sometimes this is enough to remove the discoloration.
Use a professional floor sander to completely remove the finish if the discoloration still can be seen.
Refinish the area using the same color and type of finish that's currently on your hardwood floor. This should completely restore the color.