Any backpain can be serious. I had a car accident resulting in herniations.. however, I didn't want surgery so in my experience with back pain only one thing has worked for me.
(Let me assume that as an aikidoka you have good posture)
After wasting time with physical therapists that touted the miracles of the TENS unit (Electrical impulses directed at muscle groups) and wasting time with two chiropractors (Supposedly the two best in Sacramento per news, state, and private sources. Also in retrospect I would never suggest that to anyone as one of them made me physically ill for 4 days due to his 'gentle care,' and the other actually caused me injury.). I have found that weight training is the best thing paired with back stretching a la tai chi. When I say weight training... start small, I started with resistance of 4 pounds with 10-12 reps per excercise. I'm almost back to normal now. One thing to remember though is take it easy, don't overdue it, and don't give in to frustration.