You can change the nickname used in the Battle of Warships.
The change method is different between Android and iOS (iPhone, iPad).
1) Change your nickname using the Play game. Open the Play Game app and touch “Profile”
2) Touch the “pencil mark” on the upper left
3) Enter your nickname
iOS (iPhone, iPad)
1) Open “Game Center” from “iPhone or IPad Settings”
2) Enter your nickname