Definition: the part of the face or head that contains the nostrils.
In the video (courtesy of Jennifer Morales) above, the mother fingerspells "nose" in an ASL sentence, "Where is 'nose'?". The baby Amelia (age 1;3) replies by signing it.
Children, whose first language is ASL from birth in a native ASL-speaking family normally can understand fingerspelled words, in the same way children do in an English-speaking family.
Proximalization: in her early phonological development, the baby Juli (age 1;1) tried to reach the nose as accurately as possible when signing NOSE. Another noticeable thing is that she used either hands. At this stage, it's not unusual that baby sometimes switches hand before one becomes permanently right-handed or left-handed in signing.
Related post: Fingerspelling with a CAN attitude with Deaf children.