Others that have seen their dog get hurt: does it sound like his tail is permanently hurt?
IMHO I would NOT wait until tomorrow to see a vet.
Most vets will see you immediately without an appointment when you tell them the circumstances and the symptoms. There 'are' some physical ways of manipulating the dogs body that can tell you without x-rays, if the expense of that is what prevented you from having the x-rays done on the first go around.
His tail is not what you should be worried about. That's an indication that their 'could' be damage to a nerve or spinal cord injury which when treated ASAP can have pretty good recovery results IF attended ASAP.
I know how to do the physical exam to determine where/if spine injury is present sadly from being there done that a few times. But just saying take him to the vet asap and tell the vet what you observed and they will do that type of exam on him and maybe you can dodge the xray costs. Sometimes it's just as simple as to get him a shot to reduce the swelling that might be pressing on the nerve before the nerve actually dies and the dog ends with paralysis.
Keep us posted. Good Luck.