Unless your dog does it to make you fall down, it does sound like it is just for attention.
However I believe if you give in and pet or even acknoledge the nose touch from your dog, you are in fact losing a point in the dominance run. As it seems to be gentle, the best is to ignore ALWAYS. In doing so you do not lose points.
If you believe it to be more than gentle and you think it should stop you should say no to the dog just before he does it. It takes timing but just before is the best way to teach a dog not to do something. If he does it anyway just ignore.