Here's an article regarding it https://www.cbssports.com/nfl/news/bills-call-alleged-racial-slur-by-richie-incognito-a-misunderstanding/
I find what Ngakoue said interesting: On Monday, Ngakoue was asked if Incognito used the N-word. "I don't remember, but, he said what he said," the Jaguars defensive end said. "He knows what he said. I don't gotta repeat it."
I'm gonna have to side with Richie on this one.