If you have little scratches on your hardwood floors, you can use a marker or wood stain pens. The right colour is the most important thing to consider when fixing small hardwood floor scratches and minor blemishes.
If the damage is large enough to have taken the finish down to expose the wood, it needs to be repaired. If left exposed too long, the wood will be susceptible to moisture damage. Repairing a small area will save you in the long run. You should also call a professional any time you feel less than 100% confident in your ability to handle the repair yourself.
Before any repair is attempted, you must decide whether the damage is severe enough to warrant hiring a pro. Often this decision can be made by looking at the end of the damaged piece. Also, If you can make out the manufacturer guide you can know if such a repair is covered under a warranty.