Our little man is 8 months old and early on we noticed he loved to have his cheek, neck, face area nibbled!
It all started when I would wrestle with him on the floor or bed and when he started to get a little rough I would simulate another dog gently
holding him down by his neck with my mouth (sounds really weird but it's not as crazy as typing it out sounds). He would immediately calm down and he actually starts to wag his tail! After a couple times of doing this he would have seek out for us to nibble on his cheek for affection and he loves it! Pretty much when he wants attention/love, he'll climb up where we're sitting or climb over us in bed just so you can plant his head right on my mouth. When I oblige he seriously smiles and seems like he's in heaven.
Does anyone's dog do this?!?? If I had to take an educated guess he just loves the closeness and he seems to be a pretty submissive loving pup. Maybe reminds him of days with his mother/siblings?