Geralt notes that Odo's dog seems to be guarding something, but I can't figure out what any of that cutscene means. Is there any point to it?

Go back to that spot after sunset.

There should be a short cutscene playing. If you didn't get it, it's probably too early. Do a few quests for 'main' villagers first.

And no, it's nothing terribly important, just one of small tidbits that add to solving the mystery of this area ;)

This is a piece of a little puzzle that will come together at the end of the chapter. I'll drop one hint for you: talk to old ladies, all of them.