I'm Chinese, so I guess I could answer this question for you.
There are several type of nickname in Chinese
First one is what you were call by your family while you were child.
Second one is for friends calling, we don't use to call other peoples' name directory, so we use title or family name(Add Mr. or Ms.) for colleague, but for friend we use nickname.
Third one is for foreigner, lots of foreigner can't pronounce Chinese characters, so we create a nickname in English for foreigner.
In most circumstances, nickname is unlikely related to really name(Full name).