Pwesonally, I think that you first need to consider this man's behaviour and what it nay indicate.
He gets close ~ entering your personal space. This holds a message.
It could be: I'm male; you're female; I'm dominant
or I'm manager; you're staff; I'm dominant or
I like you, so if I want to get close, will you allow it?
You say that he is nice, but you do need to be sure that he is genuine and not just a flirt.
If you think that he is genuine, and you like him, then just be friendly. By allowing him to come near to you, you are already signalling to him that you like him to be close.
Don't worry about compliments, just be friendly and natural. If he helps you, say how grateful you are that he is willing to take this time helping you. Say how kind it is. As Lee said, tell him how you are getting on with the work and that you enjoy working for him. And smile!
Good luck & take care!
