They are two different words with two different meanings. nikka split off from that other word and took on a different meaning like many words do. If you truly feel they are the same word try using them both and see how others react.
Also OP worried bout the wrong shyt. Even if they are the same word and every black person on earth stopped using it, how does that lift the overall situation of the African diaspora? Will that suddenly end systematic racism and implicit bias the prevents us from having access to the same opportunities as our peers? Will that suddenly provide payment for the centuries of labor our ancestors have done in the Americas and the Carribean? We have bigger issues to worry about than this tired old argument. First and foremost reparations.Tangibles are more important for us right now. We have been extremely lacking in that department for nearly a decade.