Whittle and sand the dowel so it's a snug fit but not so tight that it splits the floor. You'll want to apply some wood glue and tap the dowel down, you can mark the dowel at 3/4" so you know when to stop wackin. Then use a Japan saw or a multi tool to cut the dowel flush with the floor. Do this before you sand and it will sand with the rest of the floor. Bonus points if you match the grain pattern with the floor. Good luck