The rolling of his top lip & making a sneezing or snorting sound is part of the mating ritual.
It is not so much a sign of aggression, but more of a "I know you are a girl, and I may be attracted to you" thing ( I am trying to put this delicately).
I just tell mine to go away when they are acting like a "man". We have a new very large Boer billy that has not quite learned to go away yet, but he keeps about 2 feet away unless I go to him.
My Pygmy billy has it figured out, and he is a little gentleman around me & GD.
They are so cute, but they can get out of nearly anything. I think they scheme all day on plans to escape.