Looks like a split off of a rim bur that altered the coin.
Why do I think that? Note the shape of the affected area? When you look down at it, there is not wave like post strike damage would cause. So the item struck through was prevented making a wave because the die was enclosed, the planchet was enclosed. A struck through an object leaves a wavy from metal movement because the die prevents this wave from happening:
Scratches make a pushed aside area like moving snow in the winter:

Because if was not in the die when this happened, the metal is displace in a movement direction on the coin.

Note the metal movement is a different direction of the dies.

You can see the wave affect on this coin that was probably damaged by a spent 22 shell. Note the distortion?

This just damage to the coin. The rim metal is move in a direction the coin was not struck.
PSD.

Damaged from a ball point pen.

On your coin it is contained, so it is a struck through error. Rim bur.
Pressed with something.