Where is he hiding? In his plants or does he have a little cave or something to hide in? It's strange but the more hiding places a fish has, the more confidence it has and more it will be in the open. Just knowing they CAN hide if they want makes them not want to. That said, I'd say he's still just very shy and settling in.
My new girl was very much like that when I first got her. The moment I got near the tank she was off darting around like I was the swamp monster. She was so afraid of me she wouldn't come up to the surface to eat and I got so where I was afraid she wouldn't come up to get air either. But I spent a lot of time by her tank, sometimes just putting my face close and looking at her, sometimes putting my hand on the glass or even inside the tank. After a looong while, she realized I didn't mean her any harm and I even brought food and she started to swim around more. It really does take a while but just spending as much time near the tank is the best thing. Pull up a chair and watch TV or read a book. Once he realizes you're not only still there but you haven't harmed him, he'll come around.