How to remove a nickname from a group but keep yahoo ID?

I am in a wonderful group. When I signed up I used a specific nickname, not a yahoo ID. Now I don't won't to use that nick name but I want to remain in the group and keep my Yahoo ID. I have gone thru my account, profiles etc. and have removed the nickname in every area I have seen but it keeps reappearing in my group posts. I have changed everything I can think of. Help!!!!!!!!!