There are many good suggestions listed above -- but just remember, every case is a bit different. I have tried most of the alternatives suggested and some have worked while others haven't.

Personally, what helped me was doing core exercises (that can be yoga, or stretching, or crunches). But you may have to wait for your back to heal a bit before you go hard at it. I have found that back immobilization doesn't help, and that continuing to move (particularly walks and swimming) when my back starts to ache seem to help. But that is me. You may have to figure out what works for you. And that may take time.

There are a lot of cyclists on this board that have had back pain and continue to manage it. Some have had surgery, some are in PT, others work out -- my opinion is just keep trying things until you find something that works, have patience, and be prepared to manage your back for the rest of your life.

Good Luck! Being off the bike is frustrating, so be patient, you will be riding again.