Hiya Game. There are actually quite a few people who have had the exact same problem - game crashes while purchasing, then you can't get in at all from that device ever again. You probably can log in from a friend's phone or iPad but that doesn't help much.
So far, I've only heard of a complete factory reset working to fix the problem - it's a tough pill to swallow though. You can give that a shot or keep your eye on the forum here. Eventually someone might find and report a fix... maybe.