Both my dogs 'poke' me when I am sitting down, mainly on the arms, hands or legs. For them, it is their way of saying they want to be petted and have attention. It doesn't bother me with them, since neither of my dogs are dominant types.
Usually I try and initiate the petting sessions, but Nova (my border collie), isn't really the cuddly type. Usually she's happy with just a quick hello pat, and she's off to do her own thing. So when Nova pokes me, I'm quite happy to give her some attention. It's a treat for me
Cody, my 9 year old Aussie is a different story. He is too pushy about it, so I will ignore him when he is trying to get attention. He will also poke me when he is hungry and wants his dinner. Having a set feeding schedule helps with this.