How to play this flush draw?

[Beck]

Bodog 30+3 Blinds 50/100

SB 1050
BB (hero) 1555 - is dealt [img]/images/graemlins/diamond.gif[/img]J [img]/images/graemlins/diamond.gif[/img]K
UTG 2340
UTG1 515
MP 1675
CO 1140
BUT 1725

3 folds, CO raise to 200, BUT calls, SB folds, Hero calls

Was calling PF a mistake?

Flop (pot 650)
[img]/images/graemlins/diamond.gif[/img]3 [img]/images/graemlins/diamond.gif[/img]T [img]/images/graemlins/heart.gif[/img]6

Hero checks, CO bet 420, BUT calls, hero????

DO I just let it go? Should I have led out the flop?