Your nickname should not be from someone you don't know picking it. My campers gave me the nickname "Weeble Wobble" because I fall down a lot, like weeble wobbles do. your nickname should be something that defines who you are. nicknames are supposed to be realted to you, and the person should be able to tell you why you have that nickname. Nicknames should not be something that you think of, but should be something that someone else thinks of for you. your nickname might not come for a while, but someone will start calling you something because of something you said or did and it will sorta stick.
hope this helps.