There are a few ways to approach your undercuts.
If the head is actually made of 2 parts, you can use the Smoove tool from the Sandbox extension. Usually Smoove does its thing along the blue axis. But Smoove + Shift lets the tool work perpendicular to a surface. Take a look at this Kitty. In that case, the Smoove tool works on a 3D shape because the cat is low-poly and the Smooving radius is set fairly small. The Smoove tool does not just work on the surface you place the tool on, it will also move any surfaces behind the surface you are adjusting. So the Smoove tool cannot just be use on the rhino undercuts if the rhino is one piece. But give it a try and see if it can work. And the Artisan plugin I linked to in the Kitty example should have a tool that would work.
You also could replace the eye and nostril with new geometry. Cut out the eye and nostril. Position a spheroid model in place and intersect the parts.
You could also Push/Pull new eye socket and nostrils. First you need to delete the undercutting geometry. It needs to be a clean cut so a flat face is formed. Position a circle or rectangular face where it would make a nice cutting plane. Select the cutting plane and rhino > r-click > Intersect. Delete the old undercutting geometry and unneeded outer edge of the cutting plane. Then you can use Push/Pull and the Scale tool to make new sockets. The method is similar to shaping this kidney bean
except you don’t have any Arc cardinal points to adjust the outer perimeter. Though if you want, it would be possible to add cardinal points if you get creative