KQo - Who's raising the river?

[synbad13]

No reads on Villain

Party Poker 2/4 Hold'em (10 handed) converter

Preflop: Hero is MP3 with Q[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/club.gif[/img].
<font color="#666666">3 folds</font>, MP1 calls, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises</font>, <font color="#666666">2 folds</font>, SB calls, <font color="#666666">1 fold</font>, MP1 calls.

Flop: (7 SB) 4[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, MP1 checks, <font color="#CC3333">Hero bets</font>, SB calls, MP1 folds.

Turn: (4.50 BB) 3[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, <font color="#CC3333">SB raises</font>, Hero calls.

River: (8.50 BB) Q[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets</font>, Hero ?.

I'm thinking maybe he has a set... did I let nightmares of a big hand keep me from re-raising? Regardless of what he showed down, he could have made a str8 although that's unlikely and I now beat other 2pair hands. I sure don't want to get 3bet

What would you do on the end?