I'm seeing a new small hole on my hardwood floor since last week. It almost looks like it was a black spot before and then it became a hole. Is this because I didn't maintain the floor? or is it some sort of insect that did it?
It's likely a knot that came loose. The circular grain around it sure makes it look that way. The wood can turn blackish like this if water gets in there and sits which could easily have happened with a small hole like that.
How a Pin Knot is formed. Broken branch with encased dead twig, when the branch split under snow load, the twig slid through the surrounding wood, surviving intact. Same thing happens on tree trunks when small branches die and don't break off.
Clean out the loose or soft darkened area with a utility knife.
Fill the hole with stainable wood filler that is close to the shade of the floor, such as this
After it dries, if you need to color it to blend in, try one of these markers.
If necessary, make it just barely darker than the surrounding wood. It will look like a small knot. The colors can be blended by putting small dots of diferent colors next to and over each other. Go slowly.
Seal it with a touch of polyurethane with the same sheen as the rest of the floor (it looks like a satin finish in the picture).
Black holes are caused by a massive body collapsing in on itself, creating a dense object with a gravitational field so strong that the escape velocity is greater than the speed of light. Or, a knot falls out.
I'd drill out the dark matter around the hole, and fill it with a dowel to about 1/8 below the floor surface. Then I'd do my best finishing the top with wood filler.
If more holes appear, then check for various woodworms, wood beetles, fungus, and mould. Sometimes, larvae create a symbiotic relationship with fungus. Treat wood by removing polyurethane finish, or drill a bit. Apply boron, creosote (not appropriate here), LOSP, or CCA (not appropriate here). Seal.
Get a dehumidifier to reduce relative humidity to at least 50%. Vacuum at least every 5 days, and avoid "dead" products, such as down, feathers, wool, silk, etc. since they can create a favourable environment for other pests.
Agreed, replacing the panel is best however it is a lot of work. An alternative is to use a reamer cutter (a sort of parallel cutting tool-make sure you can get a plug cutter of the same size or slightly larger)slightly larger than the blemish. Cut in at appx 45 degrees in line with the grain. Cut a plug from scrap, with good waterproof glue (Cascamite is good) tap the plug in well moistened with glue GRAIN ALIGNED with the board. When set use a sharp chisel to 'nip off' the end of the plug and finish with fine sanding and local refinishing of the floor. One will be left with a barely noticeable oval plug grain matched to the surrounding floor.