I kind of wish he hadn't run into his classmates and the teacher. It was more interesting to see him roam around and pick up new people and fight tough enemies.
Even if he somehow had found the materials for it and the knowledge to make it, would he be insane enough to use it a few kilometers from himself and how exactly would he use it ? I mean, he's pretty strong, but throwing a nuke by hand ? And at this time, he hasn't made anything larger than the humvee, and to launch a nuke... yeah