Bad play preflop, but what about postflop?

[Derek in NYC]

10/20 half kill live. Its pretty late at night, table is reasonably tight. CO is loose but plays okay after the flop, probably stealing with semi-light raises. BB is tight preflop, somewhat aggressive post-flop, but will calldown with a reasonable hand if you show aggression back.

Folded to CO who raises, button folds, I'm in the SB with AKo and I call (rather than re-raise), BB calls. (A reraise is better against a likely steal, no particularly good reason for my lame play.) Flop comes AA7r, I bet, BB raises, CO folds, I call. I check, BB bets, I raise, he calls. River comes 5. I bet, he raises, I call.