10nl 6max: Top pair on river, readless, no idea what to do

[a nonymous]

$0.10 BB (4 handed)

BB ($6.45)
Hero ($17.70)
Button ($8.90)
SB ($9.85)

Preflop: Hero is UTG with A[img]/images/graemlins/diamond.gif[/img], J[img]/images/graemlins/heart.gif[/img].
<font color="#CC3333">Hero raises to $0.35</font>, <font color="#666666">2 folds</font>, BB calls $0.25.

Flop: ($0.75) 3[img]/images/graemlins/club.gif[/img], 7[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">BB bets $0.3</font>, Hero calls $0.30.

Turn: ($1.35) 9[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">BB bets $0.5</font>, <font color="#CC3333">Hero raises to $2.05</font>, BB calls $1.55.

River: ($5.45) 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
Hero ?

I had no idea what to do, couldn't put him on anything other than a weaker ace, but that still didn't make much sense. No reads/stats beyond that.