gnaw (gnaws 3rd person present) (gnawing present participle) (gnawed past tense & past participle )
1 verb If people or animals gnaw something or gnaw at it, they bite it repeatedly.
(=chew)
Woodlice attack living plants and gnaw at the stems... V at/on n
2 verb If a feeling or thought gnaws at you, it causes you to keep worrying.
WRITTEN
(=nag)
Doubts were already gnawing away at the back of his mind... V at n