If you suspect a back or neck (spinal) injury, do not move the affected person. Permanent paralysis and other serious complications can result. Assume a person has a spinal injury if:

• There's evidence of a head injury with an ongoing change in the person's level of consciousness
• The person complains of severe pain in his or her neck or back
• The person won't move his or her neck
• An injury has exerted substantial force on the back or head
• The person complains of weakness, numbness or paralysis or lacks control of his or her limbs, bladder or bowels
• The neck or back is twisted or positioned oddly

If you suspect someone has a spinal injury:

• Get help. Call 911 or emergency medical help
• Keep the person still. Place heavy towels on both sides of the neck or hold the head and neck to prevent movement
• If the person shows no signs of circulation (breathing, coughing or movement), begin CPR, but do not tilt the head back to open the airway. Use your fingers to gently grasp the jaw and lift it forward. If the person has no pulse, begin chest compressions
• Keep helmet on. If the person is wearing a helmet, don't remove it.
• Don't roll alone. If you must roll the person because he or she is vomiting, choking on blood or in danger of further injury, you need at least one other person. With one of you at the head and another along the side of the injured person, work together to keep the person's head, neck and back aligned while rolling the person onto one side.

Source: https://www.mayoclinic.org/first-aid/first-aid-spinal-injury/basics/art-20056677