AA on 999 board

[WhskyRiv]

Villain is 50/7/2...should I have just called flop?

Full Tilt No-Limit Hold'em, $0.25 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

SB ($25.65)
BB ($35)
UTG ($30.05)
MP ($13.50)
Hero ($26.30)
Button ($35.90)

Preflop: Hero is CO with A, A.
[color=#CC3333]UTG raises to $0.85</font>, [color=#666666]1 fold</font>, [color=#CC3333]Hero raises to $4</font>, [color=#666666]2 folds</font>, BB calls $3.75, UTG folds.

Flop: ($8.95) 9, 9, 9 [color=#0000FF](2 players)</font>
[color=#CC3333]BB bets $7.5</font>, [color=#CC3333]Hero raises to $19</font>, BB folds.

Final Pot: $23.95