Tough decision at the bubble

[babaorumi]

Hi !
I played a sng 5$ on UB yesterday and I have been knock out 4th with AKs :

So we are yet 4 at the table, blinds are 75/150.
OTB : 2500
SB : 2500
BB : 5000
I : 5000

I am UTG and I held A [img]/images/graemlins/diamond.gif[/img]K [img]/images/graemlins/diamond.gif[/img]

I raise 3BB or 450.
All fold exept BB who calls. BB seems a tight player.

Flop : 8 [img]/images/graemlins/club.gif[/img]K [img]/images/graemlins/spade.gif[/img]7 [img]/images/graemlins/spade.gif[/img] (Pot : 975)

BB check, I bet 600
<font color="red">BB raises 1200.</font> Pot is now 2775.

What should I do ?
Yesterday I shoved all my chips and have been eliminated against pocket sevens which caught set.
I know that my all in was not good play because I'm called only by a set.

What is a right play ?
On one hand, I have top pair, top kicker and I can't think I'm beaten every time I'm raised.
On the other hand, I'm against the big stack who covers me, we are near the payed places, and BB is a solid, conservative player.

Thanks for your answers or opinions.

P.S. My english is perhaps poor, sorry, I'm learning !