I have a house that is roughly 100 years old with hardwood floors. We purchased the house about 5 years ago and immediately got the floors resurfaced. Even before resurfacing the floors I noticed that there was a small hole on one of the boards that didn't go all the way through but seemed to be getting larger overtime. I was wondering if anyone had any recommendations on how to repair this hole. It seems that the hardwood is almost hollow where the hole is happening. Is it possible to fill it in with wood glue or another product such as a sawdust mixture? I would prefer not to replace the board. Any tips would be greatly appreciated.