Burned foot is mostly OK now, just need to fasten my shoe a bit looser as otherwise it puts pressure on the blister that formed.
I never slept last night, not a wink due to pain & effective treatment. At least four times I sat outside the shower recess with my foot inside it under a slow stream of cold water for up to 30 minutes at at time.
This was interspersed with use of a sunburn-relief aloe vera extract spray between dunking episodes.
Virtually pain-free today except when the shoe put pressure on the blister.
Greatly relieved.