Raised after flopping TP w/ AQ

[chopchoi]

.50/$1 NL. I bought in for $50. I have been at the table for one round, and my table image is laggy. So far I have won 3 pots uncontested. Twice with a bet on the flop. The hand right before this one, I won pre-flop by coming over the top of the pf raiser. I now have about $62.

I raise to $4 from MP with A [img]/images/graemlins/heart.gif[/img] Q [img]/images/graemlins/club.gif[/img], and get one caller. The caller has about $140, and has been paying pretty tight.

Pot is $9.

Flop: A[img]/images/graemlins/spade.gif[/img] K [img]/images/graemlins/diamond.gif[/img] 7 [img]/images/graemlins/club.gif[/img]. I bet $7. Villain raises to $21.

What do I do?