If someone had a mild cervical spinal cord injury but they were still able to walk, could they still die directly from a spinal cord injury? or would the injury have to be severe and they were paralyzed for them to die from a cervical cord injury?

In the absence of post spinal cord complications of limb weaknesses and no disturbances in bodily functions, you are not at risk for future dire complications.

The severity of a cervical spinal cord injury varies depending on the extent of cord damage and the level afflicted. If this is a high injury at C3 or above, the phrenic nerve compromise could result in apnea and subsequent demise. Cannot be more precise without numerous specifics.