I am not ruling our pain, but usually happy dogs will exaggerate their pain for attention, but maybe he's psychologically hurt by the incident? And all the fuss you're making over him now?
Years ago a broom tipped over clocking Coco right on the head and for years he would refuse to walk past a standing broom. Even during play he would simply halt and carefully avoid it.
Another test is to gently-moderately press on all the segments in his tail one by one, oh my goodness talk to him and praise him for letting you do this!! and watch for any sensitivity in his body language. After wards give him a treat!
Maybe talk to your vet about a sample dose of Metacam. It kills pain. If you notice a difference in his behavior after it then ask for further treatment options. Bless and good luck!! Rooting for the little guy