gnaw

To bite something persistently, especially something tough.

The dog gnawed the bone until it broke in two.

Ten thousand men that fishes gnaw'd upon

To produce excessive anxiety or worry.

Her comment gnawed at me all day and I couldn't think about anything else.

To corrode; to fret away; to waste.

VVots thou vvho's returnd, / The unthrift Bonvile, ragged as a ſcarre-crovv / The VVarres have gnavv'd his garments to the skinne: […]

The act of gnawing.

have a gnaw of a bone