To add to this there are also methods and processes to assess the likelihood of a spinal injury and how safe it is to move them - patient assessment, age, mechanism of injury, alertness of the patient and their willingness to move their neck etc. However if you’re not trained or you have doubt its best not to move them if they are in a safe position.
It’s called triage. The van driver is at worst a “green” (lowest priority) so your priority should be with the patient with more serious injuries. That’s not to say just ignore the other person completely in case their condition deteriorated, but just an occasional eye is likely to be fine.
And well done the OP, too many people just move on by in an incident so good on you for stopping. If you haven’t already perhaps consider doing a first aid course, the more advanced the better. It’s always worth having the skills and knowledge to be able to help in situations like this.