Show de User Name that create a new field collection item

This information isn't usually saved. You may be able to use the author information from the host entity. This is more likely to work if it's set up so each edit creates a new revision of the host. Otherwise you would need to set up a field and add some custom code to save the information, possibly by making the field hidden and giving it a default value in a form_alter() hook.

Hope this helps.