Nachi-Cocom was closed by the authorities BEFORE the hurricane arrived for alleged environmental damage. It was damaged by the storm as well and has not re-opened since. There have been constant rumours that it may re-open, but I've been past recently and it looked a long way from being ready still.
There are still plenty of other great beaches to chose from though - you can find some good information on this Cozumel news
website - scroll down to the Beach Club Update on 17 March.
Hope that helps...!