I accidentally used the n word today at work
Really? Why would you use that word at work?
It's just something I do not care about
Regardless of whether you think it's a big deal or not, you should still be careful.  Saying things like that at work can get you fired!
I'm fine, I think my colleagues are fine with it. They don't seem bothered by it.
It doesn't matter if they weren't bothered by it this time, the ones who were bothered may just feel too uncomfortable to speak up. You need to never use it again and be more careful about the words that you say at work.