My partner (25M) uttered a racist slur while sleep-talking - what should I (22F) do?

[CW: racism]

Hi everyone,

Posting this under an alt because I am so worried and don't want to explicitly call anyone out yet.

I really love my partner and we tend to be always on the same page politically. I'm white and he is also white fyi. Neither our conversations, nor his general reactions to political issues ever made me think he was anything less than progressive to the bone, there were no red flags whatsoever. However, recently something happened that changed all of that. He has a habit of talking in his sleep. Usually his sentences don't make sense, as is the case with other people who talk in their sleep. But last week, I was first waking up, and he was sound asleep, and seemed to be moving a lot in his sleep - I thought he was in a bad nightmare so I decided to check in with him as he sometimes struggles with bad dreams. When I sat up I overheard him mutter something that sounded vaguely like the n word so I leaned in to listen and he kept talking and I swear he again said the n word clear as day. It was enough to make my blood run cold and I had trouble falling back asleep.

The next morning I mentioned to him that he thrashed around and muttered a lot in his sleep and asked him if he remembered what his nightmares were about and he said that couldn't remember anything about his dream .

I am not sure what to do now. He has never said anything remotely racist to me or any other person in the real world - he has never said anything problematic to me regarding race before, not even joking or accidentally and I have known him for years. However, the incident has kept me in a nervous tension and made me question whether he really is the person I have known him to be, or whether he is harboring beliefs he has never shared with me. I mean, even the possibility of it being true is terrifying and I have cried quite a lot over it. I really don't think he is racist at all, but that is a huge word to be throwing around even just in your sleep.

Should I confront him about it? And if so, how do I even approach this kind of situation?