What is this black spot inside my belly button ? I am 7 weeks post op MMO. (photos)

It is very difficult to say for sure what the dark spot is based on a picture. The most common things that occur at the belly button during the healing process is a small wound or delayed healing. This usually does fine with some local wound care. It could be nothing more than a small scab and needs nothing. I recommend seeing your surgeon and he can help navigate this with you.

The pictures are not clear but it does not appear that your belly button is dead but maybe a small portion of it is dead (necrotic), if this is the case it should heal with just a little wound care over the next few weeks.   Follow up with your plastic surgeon for advice.