Ni-ni is a slur used to describe Blacks in a derogatory way. Used instead of "nigger" in potentially sensitive company, to avoid being overheard, or to appear politically correct.
The word Ni-ni is a racial slur that has been used historically to degrade and dehumanize blacks. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to blacks. If you are unsure about whether or not it is appropriate to use the word Ni-ni, it is best to err on the side of caution and avoid using it in any situation.