Babies aged 6-12 months, usually do this because of great curiosity. because when a baby pulls hair and pinches, s/he basically wants to know how you respond to what he's doing.
Babies do this to see the response and learn it. if this behavior is repeated try to give a verbal explanation.
Such as saying "No" while shaking your head. Next, raise your hand, for example, pulling your hair and explain that you don't like it by saying "No". when the baby has changed his actions, give praise, a smile, or a hug.
Then, when a child pinches because he can't get the words out to explain his feelings, it's best to try to deal with it calmly, don't get carried away immediately.