oh dear god i hope that isnt cum, and yeah glue would be your best betand maybe talk to a local texch on how to distiguise the crack
What a stupid place to put a control knob on a hollow body guitar!
I would suggest PVA or a specialist wood glue to glue the wood back on.
Try filling any cracks left with a putty filler (car body filler) and sand it down. Try t-cut or turtle wax to try and buff it back to a nice finish.
Dave Mustain has wrote some of the most amazing solos...
That he can't actually play!