So are we talking lumbar spine, sacral region or coccyx?
If its sacral or lumbar, then something can be done, but coccyx is leave it alone territory according to UK medical professionals!
I know is I aggravated mine in an uphill sprint a month or two back. Saw a professional and was told not to do anything to aggravate it, ie only gentle cycling. I felt that if I got tired at work etc my posture would start to slump/slouch and I would put more strain on it, continuing the aggravation.
Its gone now I'm glad to tell you, but just listen to your body sit up right and do some generalised core work ala tapeworm's suggestions above and try not to do too much energetic cycling. My issue was though to be the piriformis pulling too hard on the lower coccyx causing an aggravation. Stretching of all the musculature in the area will help the problem too.
I'll try and put a core routine together for you if you would like, as I used to run an hours core stability class for fellow cyclists, but might have to drop some of the exercises if they hurt or are and awkward position to get into with the injury.