If you are really asking what the first problem that Jonas faces is, I would say the problem is how he will fit in to his society. He is specifically worried about what job he will be assigned to at his Ceremony of Twelve. At this point in the story, all he is really worried about is being a good member of the community.
But after he is selected as the new Receiver of Memory, his conflict soon changes. Now the conflict is between him and the society as he finds out that he does not like the contrast between the things he sees in his memories and what he sees in his actual life.