If your floor is natural unstained wood then try a few types of floor urethane on your test patch.
How to fix a low spot in a wood floor.
This requires using a laser level to pinpoint the low areas and attaching the shims working on bare joists above a basement or crawlspace by gluing and screwing them to the joists.
Set the front end of the saw s flat blade plate on the damaged board with the blade held up off the surface and pointing in the same direction as the length of the floorboard.
Water based urethane will dry clear while oil based formulations will impart a slight golden.
It can also serve as a vapor barrier.
It s used to help insulate absorb sound and reduce wear on your floor.
If you need to bring down your subfloor you can try either a hand plane or a power sander.
Start the saw and lower the blade into the wood.
High spots and bumps in subfloor.
Use an underlayment floor leveler or floor patch product to fix low spots in a wood or concrete subfloor.