In 2012 an mri stated that my wrist showed associated bone oedema. what does that mean?

Hard to say: without knowing why you had the MRI. My guess is that it was an early sign of osteoarthritis, unless there was an injury and it was a local reaction to the injury. Either way it might be related to wrist pain developing now. You might want to return to clinic for an evaluation.

Injury: When a bone is bruised it swells much like skin. Some also associate this with micrfractures. In any event it takes time to heal.