I am readying my mother's house to sell and looking to patch holes that were drilled in the hardwood floors, without tearing out or having to replace the floor.
Thanks for your question and welcome to the community!
Depending on the size of the holes in your hardwood floors will determine how much materials will be needed to cover and fill them up.
For example, small nail hole and similar size holes can be covered by with wood filler or wood putty.
Anything larger than the size of a quarter, will need replacement wood in its shape to be placed into the hole. If not, the putty or filler won't hold onto it, leading to failure and it just not working.
Grab a plank of hardwood floor that is similar in width and depth that looks like or is the finish you have. Cut out the size you need, and simply install it into the hole. You can use wood glue to fasten into place. After the glue has dried, you can use the filler or putty to cover up the cracks.
While you can't completely eliminate the hole that is there, you can cover it and fill it.
Let us know if this has assisted you, and let us know if you have any further questions.