The dilemma lies in Huck's decision to turn in Jim, a runaway slave who belongs to the Widow Douglas, or to keep his mouth shut and allow Jim to escape.
This would not have been a dilemma for Huck had they not spent so much time together on the island and the raft getting to know one another. Huck grew up believing that black people were meant to be owned and live their lives as slaves and white people were meant to own them. Getting to know Jim, Huck now recognizes him as a living, breathing, thinking, feeling PERSON. The fact that he is black is now almost irrelevant. Huck considers Jim a friend...not just property someone he knows owns. However, the dilemma is that he feels a responsibility to his heritage and to Widow Douglas AND his new friend, Jim. He elects to go with friendship and risks his own afterlife in order to allow Jim to follow his own dreams.
Huck’s dilemma is whether or not to turn Jim in, a black slave that had ran off with Huck from Miss Watson. During the 1800s, running off with an escaped black man would be the most despised crime that anyone could commit. As Huck grew up, he learned that black people were meant to be owned and to live their lives as slaves and nothing more. This thought changed when he escaped with Jim. He began developing this moral dilemma after spending so much time getting to know each other on Jackson’s Island. Huck recognizes Jim as a person that lives, breathes, thinks, and feels. Huck becomes Jim’s friend and as a result, Huck keeps his mouth shut and allows Jim to escape. This decision is also crucial in Huck’s growth because he putting his life at risk for the benefit of Jim’s.
Huck's moral dilema falls into the category of "god's law-vs-man's law" (to borrow from Antigone). For example he KNOWS it's wrong to lie (God's law), but he also knows that Jim isn't a piece of property (man's law). So, he has to wage a war with his own conscience about whether he will uphold what is morally right in order to do what feels right. He decides he will "go to hell" in order to protect Jim and gain freedom for both of them.