Ok, its easy to fix while you have the whole dog head right click> select Isoparm> once it turns yellow go to your edit nurbs menu and hit detach. This will cut you head in half. You might have to select the isparm 2 times and hit detach until it becomes 2 parts.
that should help.
Kurt
I am enough of an artist to draw freely upon my imagination, knowledge is limited, imagination encircles the world. (Albert Einstein)
https://www.artstation.com/kurtb