Hmm, I haven't been to uni either, but I've done TONS of research because I'm going there in september, YAY! Anyway. If he is a bit immature, maybe a bit impatient and scatter-minded and has other things than school on his mind, I could imagine him just have studied stray courses, like not an actual program, but just some courses here and there. One course in sociology, one in foreign cultures, one in medieval history, one in soccer history, one Spanish course for beginners... Something like that.
If he is caring and social, maybe something like sociology would suit him and then working with ... I don't know what the job title is called in English, but working with families with troubles, a social worker? He could still be unserious and immature on his free time but when he is on the job he is super serious and caring. Or at the migration office, dealing with immigrants?
Or, if he is more outdoorsy, maybe he studied something like forest plantation and now works with you know, keeping forests. Or if the novel takes place close to the sea or a lake, he could have studied marine biology and is now preserving endangered fish or something, and balancing that with being a surfer.