Have you lost your profile? If you had a link to e-mail or social network on your lost profile, you can restore it by yourself. For this, open the game, press Settings - Main Settings - Link. Then write your login and password of your social network page or e-mail, and you will be able to enter your game account.
If you didn't have link on your profile, write to technical support. Don't forget to include information about your lost profile (nickname, level, ID).
You can change your nickname in the game settings. For this, open main menu and press settings button. In the option "Name" enter your new nickname. After you press "Change" your nickname will be changed.