One of the easier ways to model this kind of humaniform geometry is to use Applications: Shape Studio: Realize Shape to (sculpt) the basic model. Use Mirror Cage inside of the Realize Shape sketch environment to make your geometry symmetrical and save yourself some work.
Because NX won’t Shell this kind of shape easily you can Extract Geometry [Single Face] and then hide the solid and Thicken the sheet bodies. I then extruded with a [Subtraction] the eye sockets and the nasal cavity. I created one tooth on a tangent plane in the front of the mouth and Patterned Feature [Along]: Follow Face [using a face extruded from that path then hidden] from a path on the bottom of the upper jaw.