Poor you, sounds like you're in shock. I'm sure the dog is fine though - my old springer got hit by a car, went right over the bonnet and couldn't use his back legs for a week but never thought twice about it. It's important that you try to be as normal as possible with him or he'll pick up on your anxiety and maybe develop worries about going out. Why can't he go for walks?
How awful, stop thinking about what might have been now, or you will drive yourself mad, he was very, very, lucky. Can you not take him out as he is still hurt? Or because you are worried? If you are worried get a long exercise lead for him, so that he can walk and be safe too.
If it is because he is not well enough yet, then lots of tug rope games are good and will not cause him to have to walk around a lot, or just let him cuddle up on your lap, most dogs are happy to just be stroked and talked to and will happily sleep more.