Left hand.. Damage between two of the metacarpals, most likely the interosseus muscles.
.. I think I'm old. I hurt myself getting into bed.
.. Granted, getting into bed in my room would be like running an obstacle course in most people's definitions, but still.
(Edit: For those that don't fully understand, it feels like being stabbed between two of your knuckles, and having someone stick the pointy end of a pickaxe into your shoulder.)