My Chinese have slightly longer 'Official' names and although they have everyday names too, they've still got nicknames.
Lord James
Officially Vectis' Lord James, Earl of Metallica but his everyday name is James.
His nicknames are Jamesy, His Lordship, Smoosh and Lord Hedgehog.
Jessie Jaye
Officially The Honourable Jessie Jaye of Metallica but her everyday name is Jess.
Her nicknames are Mad Little Fairy, Picklemouse and Mess Jess
Victoria
Officially Lilliput's Miss Lilli-Victoria of Metallica but her everyday name is Vicky.
Her nickname is Vickymouse, mainly due to her tendency to cling to your finger like a mouse. Interestingly enough, Victoria's mother was called Mouse.
Matthew C. Nobria
Officially Matthew C. Nobria, Viscount Metallica (the C stands for Crawley and Nobria was his litter name) his everyday name is Matthew.
His nickname is Mr Matthew, which is also how some of the characters in Downton Abbey would refer to Matthew Crawley, who is the character that my Matthew is named after.