I think these were nights after days when I have walked and used my legs more than usual. In the long run I am not experiencing any damage from these experiences but it's uncomfortable while it lasts.
Yesterday I went to the gym and swam ten laps - 500 yards. It isn't much but it's more than two! My left arm is far from having its full range of motion but I did not feel any pain in it during the swim. My swimming is awkward but possible. Today I swam four more laps after Aqua class and felt good about that. I call this progress and I'm hanging onto it to keep myself motivated. I do feel tired after class and I don't always feel looser or without pain but later I do seem to move better. It's hard to see and feel progress. I see it in my swimming, though, in being able to swim at all.