Well if he truly loves you, and so long as you're sure of that and know him enough to know he doesn't have any ill-intentions, then he won't want to (intentonally) do anything that would make you uncomfortable. Remember also, if you love him as a sister then you've also got to respect his feelings, don't do anything you don't want to do but at the same time understand that this must be a difficult thing for him.

So talk to him, be open, that's my suggestion. You must be close to each other so talk to him about how he feels, how you feel, set boundaries. Think hard about this and if you really don't want that kind of relationship then I think the kindest way is to just tell him that so he can move on. You shouldn't feel in any way 'dirty' about it, for a start it's him, not you. He hasn't done you any harm (I assume) and there is no harm in being attracted to someone. And I agree you shouldn't tell anyone, unless things get out of hand.