What is required of someone who shortened their hair from one side after 'Umrah, then it became clear to them that their action was incorrect?

If he did this out of ignorance, he must put on his ihram and shave his head completely or shorten his hair. His action falls under forgiveness due to his ignorance. However, if he did so based on a fatwa from a scholar, then nothing is incumbent upon him, for Allah Almighty says: "So ask the people of the Reminder if you do not know." Some scholars hold the view that shortening part of the head is like shortening the whole.