A wrong nickname was registered for me!
You probably tried to register a nickname that would have been confusingly similar to a nickname that already exists.
Such a nickname will be changed by the system automatically when registering such that the characters that are easy to confuse are removed from the desired nickname.
We do this so that you are not easily taken for someone else and are always recognized by your friends.
If you want to, you can change your nickname later on. You learn here how it works.