I screwed this river up. But how bad?

[Sykes]

Party Poker No-Limit Hold'em, $ BB (10 handed) converter

SB ($47.30)
BB ($23.40)
UTG ($24.20)
UTG+1 ($33)
UTG+2 ($21.60)
Hero ($24.40)
MP2 ($23.25)
MP3 ($21.50)
CO ($9.20)
Button ($25.30)

Preflop: Hero is MP1 with Q[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/spade.gif[/img]. SB posts a blind of $0.10.
UTG calls $0.25, <font color="#CC3333">UTG+1 raises to $0.5</font>, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $2</font>, MP2 calls $2, <font color="#666666">5 folds</font>, UTG+1 folds.

Flop: ($5.10) 5[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $4</font>, MP2 calls $4.

Turn: ($13.10) A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks, <font color="#CC3333">MP2 bets $4</font>, Hero calls $4.

River: ($21.10) 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $4</font>, MP2 calls $4.

Final Pot: $29.10

The bet at the end was a value bet/info/blocking bet. I'm not sure how 25NL plays but I don't think he'd raise me unless he had the Kh to do it with.

So how often in 25NL does a blocking bet get raised here without the nuts? Often enough to call if he does it?

Also, if I check this river, and he moves in, should I call it? Or does he only do it with the nuts?