Fold set to river shove/overbet? (25nl)

[Peleus]

Poker Stars - No Limit Hold'em Cash Game - $0.10/$0.25 Blinds - 9 Players - (LegoPoker Hand History Converter)

SB: $67.35
BB: $5.80
Hero (UTG): $28.90
UTG+1: $25.90
MP1: $26.05
MP2: $4.90
MP3: $12.95
CO: $14.55
BTN: $24.85

Preflop: Hero is dealt 4[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/diamond.gif[/img] (9 Players)
<font color="red">Hero raises to $1.00</font>, 5 folds, BTN calls $1.00, 2 folds

Flop: ($2.35) 9[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/heart.gif[/img] 7[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">Hero bets $1.25</font>, BTN calls $1.25

Turn: ($4.85) J[img]/images/graemlins/club.gif[/img] (2 Players)
Hero checks, BTN checks

River: ($4.85) K[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $4.00</font>, <font color="red">BTN raises all-in to $22.60</font>, Hero ????

<font color="blue"> Villain is 15/1.5/2 over 59 hands </font>

Love sets, could easily be two pair, however a straight is also out there.

Comments on way I played hand, and also do you call the river shove?

Cheers.