It could be true, depends on your insurance and if there is some kind of pre-existing condition clause in the coverage that would prevent coverage for a certain period of time.
Either way, the x-rays would be important to be seen, and even if you left them behind, new x-rays would show an old injury that may or may not be healed or healed properly that would be evidence of a pre-existing condition
The fact is you are having a problem with your spine and you need to see a spine specialist and you need to see one right away.
Since this was an auto accident, you should be able to go after the person that hit you with the car and that person should have auto insurance that would pay for your injuries.
It sounds like this was not a hit and run, so the info should be with the police department and the records about the accident.
If you don't have that info now, get in from the police right away. You might need to get an attorney for this as well, if you have to fight the driver's auto insurance company, but you attorney fees should be covered by that as well.
You really need to see someone right away, and find out what is going on, what was seen on those x-rays and you really should bring them with you as well.
Fran