My Manager Called Me N Word And Wrongfully Fired Me .

This happened last month .

I went into work and my job position was a van driver , I decided today to be a Co for the Van driver (passenger / Helper) I’d basically lead the porters and help them find cars to be moved . We left the office around 7:15pm - 7:20pm , we had went to a gas station . Now to clarify we were not supposed to do that . Had nothing to do with the fire but I wanted to state that , we got a call from our supervisor that they wanted ME back at the office . Now I knew why he wanted me back there , for another job or to be sent home ( this supervisor had it out for me if I didn’t do a specific duty ) . We go back and once I walk in I say “ I want to go home , I don’t want to do the job” in which I had the right to do so , we returned no later then 7:30 which start time was 7pm , me and the supervisor had a back and forth which wasn’t constructive . The night manager (Arab man ) chimed in and said “ N word what you mean “ , now I am a biracial man , black / Mexican . I did not lash out or act out of character, I stated “don’t say N you not black “ and told the supervisor and other prior auditor which were black “don’t let nobody say that here that’s not black “ , and proceeded to clock out . while I was going to clock out I heard “ your fired don’t come back “ and said “ wait your firing me because I said you couldn’t say that “ and he said I disrespected him ? , ( I also have 2 witnesses that were present in the building as well ). I came back the next day to speak to him about the situation and said it could’ve been handled better but he said “you tripped out when I said N- word “ and I looked at him a certain way and he smiled a bit . I then left and talked to HR they said they wanted me to come back and speak to the GM but I just don’t know what to do , just doesn’t sit right with me and I want justice for what happened . I had to get another job since then and I like the job I have now but , didn’t deserve what happened .

What can I do and what should I do?

TLDR: I was called the N- word by my manager and terminated for telling him not say it , he said I disrespected him .