Update: It’s not a fracture
Note: I thought I had posted this already (I wrote it two weeks ago, on the 20th of February), but I have just discovered that it’s still in draft.
It’s an injury to tendons (as I suspected).
I went in for my appointment with the Fracture Clinic this morning, and the specialist told me that neither he nor the radiologist saw a fracture — which is Very Good News. They’re going to make an appointment for me to have an ultrasound scan, and he said something about maybe an MRI. Stay tuned.
Meanwhile I have to treat it gently and avoid doing anything that hurts.