Get it, it's a metaphor. Nas has been living the luxury life, but now he's going back to the streets the raised him, shedding all the materialistic trappings that he's accumulated and returning to a more stripped down raw sound. "Nasty" is actually enough to get me stoked to hear his new album, only that album on longer has a title (RIP "The Good Life") or a release date, so I guess we'll just have to wait and see.
And while I'm digging this, I've seen no shortage of comments floating around the rap interwebs saying that Nas has fallen off, enough to make me think there might be a legitimate debate here. And for the purposes of this question, nasty = dope. Let's see....