Huck against Himself?

In Chapter 15, when Huck tricks Jim into thinking that he dreamed up their whole separation, Jim ends up getting upset with Huck because he was actually worried. Huck finally apologizes and when he does he says "It was fifteen minutes before I could work myself up to go and humble myself to a nigger." At this point, I think we, as the readers, get a clearer picture of the way people were expected to treat black people. It takes Huck a long time to apologize to Jim because it is something that he is unfamiliar with. However, after he is done, he doesn't regret it because he knows that Jim is important to him.