wait a day then text him or better yet, if possible, call him. yes that green button and your voice still work and for a first time, talking is a good thing. you don't have to talk all the time but hearing a girls pretty voice once in a while can be really nice. if you want to text him tonight keep the conversation shorter in length and make him want to come back for more. a little bit of an incentive to text you for a guy can really work.
I'd text him that same night. I'm not the kind of guy who likes girls who procrastinate or play hard to get. So me, personally, calling me a week later would signal that you were not really interested so I would ignore your text once it finally comes in. I would only pursue a girl who shows strong interest, else she's just likely to fade out during a date.