I know you said he's been fine since but here's my advice anyways.

Since there was no blood in the feces I'd say it was the diarrhea that maybe split his rectum a little.
I'd give him as much water as he wants. If he's not drinking much you should offer him some getorade or pedalyte, if you don't have that then just dilute some chicken/beef broth or bullion cubes in his water to entice him to drink more.

I'd probably remove his food for a day, then slowly introduce it to him again. feeding slightly less than he usually gets for a day or 2. If you want you can feed 3-4 small meals instead of 2 big meals. After a couple days of him being back his normal self I'd begin his regualr feedings again.

Hope things are still ok with him.