50nl 6m: Flop bottom set in RR pot, but the board is scary

[barryc83]

BB is 17/10/2 over 126 hands and CO is a fish at 42/2/.5 over 126 hands. First time that BB has RR pf. I know the pf call is questionable, but I'm 100% sure the fish calls too. Fish is type of guy who stacks off on Axx flop w/TPNK. So I figured I had good implied odds here. The flop is good and bad b/c obv AA/KK are a good part of BB's range here and the flop check is suspicious. Of course he could have QQ here or AK. I'll stack AK here and won't get anything out of QQ. Just curious as to how you guys proceed w/ this hand here.

Poker Stars
No Limit Holdem Ring game
Blinds: $0.25/$0.50
6 players
Converter

Stack sizes:
Hero: $50
UTG+1: $34.55
CO: $52.50
Button: $57.35
SB: $50.90
BB: $49.75

Pre-flop: (6 players) Hero is UTG with 4[img]/images/graemlins/club.gif[/img] 4[img]/images/graemlins/diamond.gif[/img]
<font color="#cc0000">Hero raises to $2</font>, UTG+1 folds, CO calls, 2 folds, <font color="#cc0000">BB raises to $7</font>, Hero calls, CO calls.

Flop: A[img]/images/graemlins/diamond.gif[/img] K[img]/images/graemlins/heart.gif[/img] 4[img]/images/graemlins/heart.gif[/img] ($21.25, 3 players)
BB checks, <font color="#cc0000">Hero ???</font>