Much like the line from star Trek the undiscovered country; maybe not all races have nipples in the same place. (Obvs the quite from the star trek movie was "not everyone keeps their genitals in the same place" after the big guy in prison was kicked in the knees).

Drax is not human, just humanoidesque, so maybe what he calls nipples, we call it something else

(Not based on any verified source and completely a personal theory)

Much like the line from Star Trek VI: The Undiscovered Country; maybe not all races have nipples in the same place. (Obviously the quote from the Star Trek movie was "not everyone keeps their genitals in the same place" after the big guy in prison was kicked in the knees.)

Drax is not human, just humanoidesque, so maybe what he calls nipples, we call something else.

(Not based on any verified source and completely a personal theory.)