Graham: good to hear that you didn't get a broken wrist. I think Janets advice is great BTW so if anything suggests you have a ruptured tendron please see a doctor. A few weeks away from practice is far better than a lifetime of injury.
I find that nikyo is the greatest technique for teaching us to feel and adapt to pain. It can be intense and especially for beginners it is very painfull. as you get better your body will react to the little signs of an aproaching nikkyo and will try to absorb the power through posture change and relaxing the muscles. Now if we can only apply this feeling to the rest of the body all the time...
Nikkyo between beginners is like two people yelling at each other - between more experienced aikido ka it can be like a suttle debate where the powerful arguments are just hints to read between the lines. (credit for this mental picture to my former dojo-mate Jens. A great aikido-kan and an even greater teacher)