Cut something/Cut at something

It was as though freezing water was rising in his chest, cutting at his insides.

What is the difference between "cut one's insides" and "cut at one's insides"?

What is the difference between "cut one's insides" and "cut at one's insides"?

In "cut one's insides" "insides" is a noun and the object of "cut", i.e. the insides receive the action of cutting.

E.g. "The blade of the knife cut my finger."

"at one's insides" is an adverbial modifier. It indicates continuous or continual attempts to cut in the direction of (or to) the insides - the context will say how successfully.

E.g. "He cut at the rope with his knife but the blade was blunt and he made little impression." "He cut at the rope and quickly severed it."

It is worth noting that "to cut", in the example, is used figuratively = "to inflict pain as if by a knife."