Have you had a change in your working setup recently?
Do you know how injured or niggly pulleys feel when you poke and squeeze around at them? Feels like that but on and near this particular vertebrae.
Impact from running 100km on rough ground maybe? Could just need some general maintenance as hr says, when were you last allowed to get a massage to loosen it up?
Even the vertebrae itself can feel incredibly sore when touched, even quite lightly. Massage, conditioning, foam rollering, stretching, moving around more all help.
My Mistake John M not Steve R!
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