The ornamental design for a nippleprotector, as shown and described.
FIG. 1 is a perspective view of a nipple protector showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is a bottom plan view of a second embodiment of FIG. 1, the only difference being the use of an opaque material, it being understood that all other surfaces are the same as those of the first embodiment;
FIG. 6 is a top plan view of a third embodiment of FIG. 5, the only difference being the use of an opaque material, it being understood that all other surfaces are the same as those of the second embodiment; and,
FIG. 7 is a side view of FIG. 6.
The broken lines shown on the nipple protector illustrate the environment of the claimed design as well as unclaimed portions of the design, and form no part thereof.