If you haven't linked your account to social media, unfortunately it has been lost. Try the following only, if you are sure you've linked your account to either Google, Game Center or Facebook.
- Delete the application cache and data on Android from your device's settings menu. On iOS uninstall and reinstall the app.
- Complete the tutorial.
- DO NOT link to Google, Game Center or Facebook yet.
- Link to your account using either Facebook, Google or Game Center.
If this does not help, or another account is available for linking instead, most probably there is nothing we can do to help you get your account back. Please contact support for further details.