Rhinoceros modelling problem

Hey Everyone!!

Can you help me somehow?
Anybody knows what happened with my model and how I can fix this?
The model is created in Rhinoceros. I wanted to create a cat and I've started from the head by using a sphere.
Later I booleaned the shape (boolean difference) to cut the mouth by another shape. Then happened sth like you can see in the pic below.
How I can fill the hole??
I thought that inside the head is everything filled.. so why it happened??

I've already tried to use "cap" function. But didn't hepl..

I would be really helpful for your hepl.