The phrase "gnaw at" can be defined as a persistent feeling of anxiety or guilt that is continuously bothering and troubling someone. Some synonyms for "gnaw at" include nag, prick, needle, eat away at, trouble, worry, and haunt. Each of these words can be used to describe a similar feeling of unease, restlessness, and discomfort that one may experience when something is persistently bothering them. Whether it is a past mistake or an unresolved issue that keeps coming back, the sensation of "gnawing" at something can be overwhelming and exhausting. However, acknowledging and addressing these deep-seated feelings can help one to eventually find peace and move forward.