I've got the same problem...mine is on the left side. It is only slightly sore when I walk. I have to keep a pillow between my knees to sleep and sitting is very uncomfortable after a short time. Standing up after sitting is excruciating and takes time to get fully upright from hip to knee. But I found that riding my bike is very comfortable. I don't know why as I've been told it should make it worse. It probably depends on where the nerve is being pinched in my back.
I've gone to a chiropractor 3x with 1 visit to go until we determine if I need an mri/xray. I told him I want to ride my bike and explained that it isn't a Walmart bike and that it was fitted to me at the bike shop. After promising to stay off the rough trails until we get me straightened out, he grudgingly gave permission and told me to take it easy, which I am. I'm road riding my MB but it feels good, both mentally and physically to ride.
On the plus side, it pushed me to get a road bike which I had been seriously considering anyway before this happened. Keeping my MB too because I just love the trails. Best of both worlds! Now...have you tried riding since your back started bothering you? If it feels better or doesn't bother your back, explain it to your doctor. Exercise helps us with this...and I don't know about you but if I'm not riding, I'm not getting much exercise since I can no longer jog.
Get better soon! Got a lot of riding to get done with Fall right around the corner!
Legacy2