Not sure what to do next for modeling this character

Hello! I’m extremely new to Blender, and I am attempting to model this character here.

I have modeled the button eyes and I am working on the head, but I’m not sure where to go from where I am. I want to add a jaw while being able to create a mouth cavity (I plan to rig this model for animation later on.) I also want the jaw to stay within the constraints of the current rounded-cube shape.

Here are pictures of what I have so far. I used a pre-subdivided cube (3 by 3 by 3 vertices) and a subdivision modifier (catmull-clark, 5 subdivisions.) Then I arranged the vertices, adding any needed ones (vertices circled in blue used for eye cavities.)

Any suggestions on how to add a jaw?

Ok here’s the .blend file

There are Blender Cookie Tutorials for modeling faces (including Jaws and mouth): for example.

I recommend Sculpt and Dynamic Topology for it.
Your problem seems to be getting the right topology for it, which Sculpt/Dyntopo would completely remove in place of your ability to shape it.
Your photos are blurry, so I couldn’t really tell what it’s suppose to look like but if what you’re trying to get is a round bump shape thing at the neck, then what I did was extract/extrude the bottom faces then extruded the loop from the first extract, the edge slide edges to smooth it.

I recommend using Cycles render to preview what your model looks like rendered in rendered view if your computer is good enough to do it fast enough (this is just a preference of mine because I prefer to look at a rendered image over the default display)

I also recommend modelling with the mirror modifier and not placing the objects away from the center of origin when you’re modelling; if your photos aren’t aligned, move them close enough to the center, not the other way around.

wow! never thought of that. thank you