flopped a set early in the small blind - getting some action

[Galwegian]

live mtt - $150 buyin
stacks - hero 8500, villain 7000 (starting stack was 7500)
reads: villain is a solid but not exceptional player. He has been talking about always getting sucked out on by bad players.
image: I have been fairly active so far. About 5 hands ago I showed a successful bluff to the table that won a medium size pot.
blinds 50/100

preflop - dealt to hero 2[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/spade.gif[/img]
2 limpers, hero calls, big blind checks

flop (pot = 400)
2[img]/images/graemlins/club.gif[/img] 9[img]/images/graemlins/club.gif[/img] K[img]/images/graemlins/spade.gif[/img]
hero bets 400, BB raises to 1200, 2 folds, hero ??

I'm fairly confident that he either has a flush draw or two pair. I don't think he would do this with just a king


I have two questions (obv I have my own thoughts about both):
1. What's my line now?
2. Do you play this any differently if it is a cash game?