A single engine landing with no nose gear is definitely trickier since you'll lose steering authority as the plane slows down--more danger of bouncing off to the side and flipping over, but overall I'd expect everyone to walk away from this with no more than minor injuries. The minor injuries happening when people have to use the rear escape ramps that are at too steep of an angle because the plane is nose down on the ground and the tail is way high in the air.
Chances are they'll have that plane back up in the air in a few months in regular service unless it was right on the edge of retirement already.
edit: That said, as noted elsewhere in the comments, it's pretty pointless to speculate, especially when a linked article mentions more issues than just a wheel having come off. (Although it's not unreasonable to notice that in particular, seeing as an Air Canada Dash-8 dropped a wheel on takeoff just last month.)