The cables for the landing light switch were routed over the top of the skirting-board, and had then been painted over. There's a lot of this sort of "botch it" work around the house. While the plaster was off the wall I rerouted the cables and put them in trunking in the wall. This left a hole in the floor. Usually, I'd swap out the damaged board, however here it was under the wall and I am not about to dismantle any more of this wall just to fix the small cable hole.
The offending hole.
The skirting-board has been removed.
I drilled a hole into a scrap of plywood with a forstner bit to use as a guide.
Then drill down about 4mm into the floorboard.
Cut a plug the same size as the recessed hole.
I use knots if patching pine because they are easier to match in.
The patch once sanded. I may draw in the grain, but by the time it's stained and varnished it will hardly notice.
The skirting is a mock-up, the finished article will be reclaimed wood to match the existing landing skirting.