What is the location of the Hypoglossal nerve?
The following image of a cadaver shows the hypoglossal highlighted:



 Source: StudyBlue 

You can see the flap of skin/muscle that has been removed to get an understanding of the thickness of tissues separating the nerve from outside the body.

Additionally, here is an image showing a person receiving an operation. You can see the relative depth of the nerve fairly well:



 Source: Cambridge University Press