Staying healthy costs money. Getting healthy after being ill/hurt generally costs more. Stretching, et.al. is very good of course, but if he is hurt and goes about trying to fix himself as a layman, he could make things worse (as you mention). He might stretch today and wake up tomorrow unable to get out of bed.
With a new acute injury, perhaps it is best left to professionals? Depending on how severe he thinks his injury is, should determine his course of action. A chiro will generally do limited x-rays for free (or his ins. may cover them), and it usually doesn't cost much to see them. Personally, I am a fan of DO's - almost as much musculoskeletal training as chiros and some will even do chiropractic adjustments.
There are also Medical offices that have MD/DO, chiros and PT combined under one roof. They will take a more thorough battery of images because they can bill it under the MD/DO and insurance will pick up the tab (chiros have a hard time getting reimbursed for anything but a very few simple x-ray exams).
Also, all nerves stem from the spinal cord which is housed in the vertebral column. A misalignment can cause compression of a spinal nerve at the IVF. That could result in any number of issues from numbness, to loss of motor function, to issues with organs, etc. Everything is controlled by the brain and the brain sends info via the spinal cord to those nerves to everything in our bodies.
Hope I didn't hit a nerve!