make you camera have a parent. This parent would be your actual camera position.
When it collide, your camera can not goes in.
Make a state when your camera position is not matching its parents position, it try to reach that position
(using iTween)
I suggest you to prevent that state (reach position) to do anything when your character is not moving anymore (to avoid some shaking problem)
that is how i would handle that
this is simple, you can do more complicated things.