That's what I did. Left it for the night, then deleted the app the next day and reinstalled. It worked fine the second time. Did you get your email?
Just try, leave it, try again. Being on 7.0.3 doesn't seem to make a difference. A PIN is a unique identifier for your device only. You give your PIN (a random series of letters and numbers) to people, just like you would a telephone number, and they can contact you via BBM. It's safer though, as people you barely know can't bug you or you just delete them. And being data you can use it over WiFi for free.