The second picture gives a good look at how big the dent is.
Here is another tweet, by someone onboard the Dream when it hit the dock: Twitter
The video was taken on Castaway Cay, the day after the incident. The crew started fixing the dent right after it happenned. The good news is that the hull doesn't have a hole (that was definitely intended). The Dream is still sailing as scheduled, and it is currently in Nassau again. Don't worry, they didn't hit the dock again. Hopefully this won't happen again!