You wont be screwed, dont worry! I had a very bad SIJ injury when I was 14, and I came back from it fine. You just have to appreciate that you will always have to be careful with your back, do plenty on core exercises, etc. in future.
In terms of immediate relief, Chiros are great. I imagine you are probably getting alot of nerve pain too, so nerve stretches would be good. Alot of SI injuries are due to ligament damage around the joint - this responds well to exercise, so you may actually feel better after exercises. From my experience, squats and cleans were very painful. Start at a lower weight, and build up slow!