Open the Settings app and select “Mail, Contacts, Calendars. " Scroll down and tap “My Info. " Select your personal contact, or create one if you don’t have one.
Open the Contacts app. Select your personal contact and then tap “Edit. " Change the name to whatever you’d like Siri to call you.
Open Siri by pressing and holding the Home button. Say “From now on, call me John Doe. " Siri will confirm the new name for you. This will change the “nickname” entry on your personal contact.