Re: training with an injury?!
Here's my case: I have a lower back injury(slight disc herniation) that I sustained while I was in active duty back in 1993. I discovered Ki Aikido with my kids about 18 months ago and decided to have a go at it. I had to get my doctor's permission to get into the training. What I found was the Ki exercises that we do specially the backward rolls stretches my lower back. Before, I normally wake up with lower back pain. Now a days, I don't. I have not done advanced ukemi but I have been problem free doing basic ukemi.
Having said this, I also know my limitations and don't jump to quickly into things without a quick reality check.
Get your doctor's advice before anything else.
Good luck. Oh yeah, the kiatsu press is amazing!