The lowest and softest part of the ear is called the tip or lap of the ear. See Exodus 29:20.
Related Commentaries of Leviticus 8:23
Leviticus 8:23
23 And he slew it; and Moses took of the blood of it, and put it upon the tip of Aaron's right ear, and upon the thumb of his right hand, and upon the great toe of his right foot.