Flopped middle set with heavy action (stars $50r)

This hand is from the stars $50r 2 nights ago. Average was ~10k, and I had no real reads on villains.

PokerStars No-Limit Hold'em Tourney, Big Blind is t200 (8 handed) FTR converter on zerodivide.cx

BB (t12495)
Hero (t14330)
UTG+1 (t26313)
MP1 (t14400)
MP2 (t9565)
CO (t19255)
Button (t7420)
SB (t5050)

Preflop: Hero is UTG with 5[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/club.gif[/img].
Hero calls t200, <font color="#666666">2 folds</font>, MP2 calls t200, <font color="#666666">2 folds</font>, SB completes, BB checks.

Flop: (t875) 3[img]/images/graemlins/diamond.gif[/img], 7[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">SB bets t200</font>, BB calls t200, <font color="#CC3333">Hero raises to t1000</font>, MP2 calls t1000, SB folds, <font color="#CC3333">BB raises to t1800</font>,

What is my action here? Both villains are deeply stacked, and BB is playing it like he has a made straight. Thoughts?