Extremly standard situation, what is the optimal river play?

[Melchiades]

Villain is a nit, I am a nit. So although he could call preflop with AQ, I think he dumps it most of the time. Do we push hoping to get a call from KK or the unlikely AQ. Small vbet and call a push? Flop is superdry so he has a pair+ here always, I guess he could have decided to put me on AK and call flop with a JJ or lower, but he wont be calling anything else with those hands.

Guess the problem is that my image is probably so nitty that KK is a pretty tough call for him here, since he beat nothing when I push river.

Check feels like extremly weak sauce though.

Party Poker - No Limit Hold'em Cash Game - $1/$2 Blinds - 6 Players - (LegoPoker HH Converter)

<font color="black">Hero (SB): $208.00</font>
BB: $408.30
UTG: $268.65
MP: $406.89
CO: $192.79
BTN: $174.90

<font color="black">Preflop:</font> Hero is dealt A[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/diamond.gif[/img] (6 Players)
UTG calls $2.00, <font color="red">MP raises to $9.00</font>, 2 folds, <font color="red">Hero raises to $31.00</font>, 2 folds, MP calls $22.00

<font color="black">Flop:</font> ($66) Q[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $40.00</font>, MP calls $40.00

<font color="black">Turn:</font> ($146) 9[img]/images/graemlins/heart.gif[/img] (2 Players)
Hero checks, MP checks

<font color="black">River:</font> ($146) 7[img]/images/graemlins/diamond.gif[/img] (2 Players)
Hero?