I’m not a black youth, but there is such a thing as a “nigga pass” among young(er) people. You can say “nigga” around your black friend if they are OK with you saying it. But I don’t know anyone older than, say, 40, who follows this “rule”. Most black people my age who say “nigga” have a negative reaction when white people use it, no matter how close a friend the white person may be. It’s a generational thing, I suppose.