Maybe he finds it hard to communicate hence uses pinching/ scratching to get his point across. Talk to him and explain why he shouldn't do that and teach him to use words to verbalise his feelings. My Son used to say "don't like (person's name)". After awhile we realise he is saying he don't like something that person did. So we teach him to verbalise... eg "I don't like mommy!" "U don't like Mommy to do what??" "I don't like Mommy to scold me"
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