Ouch! I wonder what it felt like when they popped it back in?
I have a friend who's shoulder used to do that on a regular basis, especially when he played rugby.
It hurts like hell initially, but once it's back in, it's not that big a deal.
It's when it keeps popping in and out with little provocation that they have to do surgery to fix it.
Seriously, as long as you don't tear the muscles or ligaments, it's not a major injury.