Yes, you can change your nickname and emoji anytime. To change your nickname and emoji, tap on the “Leaderboards” icon on the bottom of the ‘Home’ screens. The “All Access” button slides out to the right. Note you must be in Level 5 or higher to access activate or access the Leaderboards.
You can also access the leaderboards page from ‘Home’ screen to change your nickname
On the result page, tap on your name to change or update your nickname