gnaw 
/ˈnɑ:/ verb
gnaws; gnawed; gnaw·ing /ˈnɑ:/ verb 1 : to bite or chew (something) repeatedly [+ obj] ▪ The dog was gnawing a bone. [no obj] ▪ He nervously gnawed on his fingernails. ▪ Rabbits have gnawed at the hedge. 2 [+ obj] : to make (a hole in something) by chewing
▪ Rabbits had gnawed a hole in the hedge. ▪ Squirrels had gnawed their way into the attic. [=they had entered the attic by chewing a hole]
▪ Rabbits had gnawed a hole in the hedge. ▪ Squirrels had gnawed their way into the attic. [=they had entered the attic by chewing a hole]
gnaw at [phrasal verb]
gnaw at (someone) : to be a source of worry or concern to (someone)
▪ This problem has been gnawing at me day and night. ▪ She says she's fine, but I can see that something is gnawing at her.
▪ This problem has been gnawing at me day and night. ▪ She says she's fine, but I can see that something is gnawing at her.
