Walking into getting 1/4rd

[KneeCo]

PS tournament. SB is a fish. BB is a reasonable player who never seems to raise pf.

PokerStars (8 handed) FTR converter on zerodivide.cx

Preflop: Hero is Button with 5[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/club.gif[/img], T[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/diamond.gif[/img]. SB posts a blind of 400.
<font color="#666666">1 fold</font>, UTG+1 calls, <font color="#666666">1 fold</font>, MP2 calls, <font color="#666666">1 fold</font>, Hero calls, <font color="#CC3333">SB (poster) raises</font>, BB calls, UTG+1 calls, MP2 calls, Hero calls.

Flop: 6[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
<font color="#CC3333">BB bets</font>, UTG+1 folds, MP2 folds, Hero calls.

Turn: J[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">BB bets</font>, Hero calls.

River: K[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">BB bets</font>, Hero calls.


I'm fairly sure the whole way that BB has A2 and I have no idea if he flopped anything for the high. What should be my approach to the hand?