I had the wood floor chipped from heavy object played on it, removing the varnish that covered that small area. I tried to fix it by first sanding, then polyurethane on a cotton swab as the affected area was fingernail size.
Here's what it was initially:
Here's the result:
Sanded with 120 grit. Did 4 coats of polyurethane with q-tip. And the polyurethane browned it a bit. But it's rough texture and not smooth, and feels unfinished.