The ornamental design for cosmetic applicator, as shown and described.
FIG. 1 is a perspective view of the cosmetic applicator, showing the new design;
FIG. 2 is a side view thereof; and,
FIG. 3 is another perspective view thereof.
The broken lines depicting portions of the cosmetic applicator in FIGS. 1-3 are for the purpose of illustrating environmental structure which forms no part of the claimed design.