Has anyone here experienced swollen ankles after riding?

I noticed my ankles were swollen for the past week or so, enough that the top of my not-very-snug biking socks are leaving a dent in my ankle. I've never seen this before in all my years of riding. But then again, this is new territory for me (almost 61 y.o., week 9 of comeback training plan after 4 years of inactivity, recent longer rides with more climbing).

This morning, they're back to normal. Weird.

Anybody else gone through this before?