Exemple:
When I fell off my bike, I hit my chin when I hit the ground. Lucky I had a helmet on to protect my head. 
Licence photo:
CC: Attribution, Commercial Use
Regionalism:
Neutral
Regional variant:
Neutral
Full Expression:
The “in” Sound ( /ŋ/ + /g/ ) : chin
the part of the face between the mouth and the neck; where men often have beards