I claim the ornamental design for the nut chopper, as shown and described.
FIG. 1 is a perspective view of a nut chopper, showing my new design.
FIG. 2 is a front view of the nut chopper, the back view being a mirror image.
FIG. 3 is a right side view of the nut chopper.
FIG. 4 is a left side view of the nut chopper; and,
FIG. 5 is a top view of the nut chopper.
The bottom view not visible in the drawings is unornamented and forms no part of the claimed invention. Features illustrated in broken lines, including a jar shown attached to the bottom of the nut chopper, form no part of the claimed invention.