Toroid coating got scratched
From the physics standpoint, broken coating will not affect performance.

Broken coating may cause a few practical inconveniences.


This looks like an iron powder core with an enamel coating.  The coating simply prevents rusting.  So, the core will rust where the coating is damaged.  (Ferrites usually aren't coated.)  
Broken coating may have sharp edges which cut through the magnet wire enamel.  (You could smooth the sharp edges with sandpaper.)