My daughter pinched for a while, and there was also a time when she was fascinated with a mole on my neck. After a few times of telling her no and holding her hands, I followed the same advice I was given for when/if she bit: I unlatched her, set her a few feet away from me, and said emphatically 'I said no!'
Of course she cried the first couple of times, but after that, when I'd tell her 'no' when she'd start and unwanted behavior, I'd follow up with 'stop or no more me-mes'. She got that there was a consequence to her behavior.
It's a great opportunity to teach kindness, respect and boundaries as well. It's never ok to hit, and there are consequences. If he wants to cuddle and nurse, he has to be nice or he can't. Period. End of story. Nice, but firm, and nothing ambiguous about it.
By the time they are one, they 'get' the consequences/actions idea. After all, they are masters at the 'if I drop this, how many times can I get you to pick it up' game.
Around this time, I also started ideas about sharing. She still nursed at night, in the morning, naps, and when she was upset or tired (in other words, plenty), but I began pointing out that I was sharing, paving the way for when I couldn't (or didn't want to) share. By the time she was two, I could explain, 'these are MY me-mes, and I love you and will share with you, but you may NOT demand because sometimes I can't share with you'. I did this along with the principle that sharing was good and nice and it's important to share, but it is also ok to not share special things, (in addition to 'my body is my body and yours is yours'). I also always asked her 'can I kiss your nose', 'can I give you a big hug'...giving her the message she also had power to say 'no' to anyone being in her own space.
It worked great. In fact, she had one toy she was very protective of, and I would tell her, you don't have to share that, but if you don't plan to share, you must put it away because it's not polite to play with it if your friend can't play with it too. We never did have the 'MINE' issue that so many kids go through.
She also has always felt comfortable with her own boundaries and chooses who she will allow in very carefully.
K. Wildner, HypnoBirthing Instructor