Nose graft, should it scab? (photo)

The graft take is usually evident by a week if not two. Some times for whatever reason it is not clear, some exudate can distort the appearance. Often once the 'scab' is taken off the graft underneath is good. I would encourage you to see your surgeon. 
Even if the graft has not worked as well as planned there are good local flap options for that particular location of the nose, see a specialist plastic surgeon in your area.
Wish you the best in your journey.
Dr Leo Kim, Specialist Plastic Surgeon in Sydney

You should contact your Mohs surgeon for his/her specific instructions and post-care. In my opinion, scarring leads to scabbing. And I always recommend people clean the area and keep it moist. I don't want any scabbing. But you need to contact your surgeon for specifics on post-care. "This answer has been solicited without seeing this patient and
cannot be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."