I'd call my child the name I liked. I probably would consider if there were any other 'full versions' that I liked, as in - if I wanted to call my child Jo but didn't want them to be Joanne/Joanna I'd look around to see if there were any other 'Jo' names I liked, like Jolie, Josie, Joelle. But if there was nothing, then I'd use the nickname, as opposed to a name I didn't like.