The ornamental design for a nipper, as shown and described.
FIG. 1 is a top, rear, right perspective view of a nipper according to an embodiment of our design;
FIG. 2 is a rear elevation view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a left side elevation view thereof.
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dashed line portions of the drawings is included to show unclaimed subject matter only for the purpose of illustrating environment and forms no part of the claimed design. The dash-dot lines in the drawings shows represents a boundary of the claimed design but forms no part of the claimed design.