Like most people have already stated him "nosing" you isn't necessarily you being dominated. It coule be just him getting your attention. Which is ok considering the other alternatives they can do to try to get your attention.
He could sit and stare at you, which not all that bad, but it could also be considered as "challenging the alpha" and you being the alpha you don't want him to do that. Just as long as you return his stare he is the one who looks away first.
He could also nip/bite at you to get your attention. Which all together is something you want to avoid.
He could bark, which of course is not always wanted.
So out of all those things I think the nosing is the less of all the evils, just don't let him do that to you too often.
Best of luck though!