C.S.
This is a really common problem that most people will face at some point in their lives. He's by no means alone here!
I would recommend keeping his primary care doctor in the loop, and be very methodical as you go forward. If possible, get an MRI to see what the problem may be. It would be helpful information whether you choose physical therapist, chiropractor, or if more severe problems arise in the future (ie it will be a baseline for comparison)
I've had some minor problems and have had good physical therapy experience at St. Francis in Evanston. It is amazing how they manipulate your spine to give you some temporary relief! I am feeling stronger and more equiped. I've also heard great things about Rehabilitation Insitute of Chicago. My mother had severe back problems and many people recommended Dr. Liu at Northwestern downtown if surgery is ever necessary.
Good luck!