gnaw on something
to chew on something. (Usually said of an animal.) The puppy has been gnawing on my slippers! This slipper has been gnawed on!
1. To bite or chew on something, either without eating it or removing small pieces of it a bit at a time: The dog has been gnawing on that bone for days.
2. To cause someone or something to have or feel persistent discomfort, anxiety, or guilt: Unpleasant dreams gnawed on me all night and I couldn't sleep.