Nickname troubles

Ok so this really isn't related to anything on this app but I didn't know who else to ask. Anyways, I recently moved and will be going to a different high School and I thought now would be a good time for people to start using my nickname instead of my real name (I prefer people to use my nickname but never made a point of letting people know at my old school because they always called me by my real name except a few close friends). But two things bother me, how do I let a teacher know that I prefer to use a nickname (I don't want to do it front of the class because I'm kinda shy)? And also recently some jerks said my nickname was stupid so what's your opinion on it (it's Savy btw)? Thanks for your help 😁😊