It could be that teh fuel system has a breach. These systems now days are sealed (somewhat) and if vented while running can cause a CEL. That is normal for a lot of vehicles. Sometimes if you dotn tighten the filler cap after adding fuel it can come on too. So I would be hesitant in driving it, especially if you smell fuel. There could be other things that could cause it too.
Also i would bet if it was that good of a smack the the paint on the bumper is spidered. These bumpers are tough but the paint is still very fragile. Look on top of the bumper right near the rear deck. My vehicle has some spidering there too from a rear impact. Not strctural damage but the paint on the bumper is cracked. If it didnt then you got away very lucky. Certainly you need to have someone structurally take a look that the vehicle. I would hate to see you get into another accident and due to something not being repaiered cause you injury.