Is there a mask where you only need your nose to breath underwater?

Yes, an AGA mask covers your complete face and the air is supplied to a connector at the bottom of the mask supplying air to the complete interior of the mask, therefore you would be able to breath just through your nose if you would like.

there are several models, do a google search on IST, or OCEAN REEF - NEPTUNE, OCEAN TECHNOLOGIES - MANTIS, or OCEAN TECHNOLOGIES AGA - this is the one you see people using on TV documentaries all the time where they can speak underwater. They simply add a small microphone to the mask. it is also the mask used in most large Aquariums that do live diver presentations from underwater.