Could I put him on the nut flush flush?

SNG
5 handed
Blinds 40/80
Me 1700 Him 1800
I'm on the button with KQoff folds to me.
I raise 3 BB
BB call

flop KQx 2 spades
he open bet 500
I flat call (I think he just whant to take the pot)

turn x of spade
he check
I'm all in!!! I dont want him to hit a 4th spade on the river
He calls and Show AJs

Then, a miracle Q hit the river and I ended up winning that STT.

I yought to AJ or A-10 of sapdes when I flat called the flop... but after I figured he would have defent his BB more agressiveley with these hands.

And probably check raise the flop knowing I would probably bet considering I was the preflop raiser...

Should I have raise the all in on the flop?

KJ