Can I change my nickname?

Yes, from your profile settings. Your nickname starts out as the name you entered when you signed up.

After a change, the nickname is locked for 14 days before it can be changed again. Friends, clubs and leaderboards identify people by nickname, so the cooling-off period keeps names from shifting under everyone else.

Your account also carries a permanent identifier that never changes, so your history stays attached to you no matter what your display name is.