username problem

I encounter a problem while trying to change my username from the users and groups settings in the administration panel. I changed my username to another once and now would like to change back to my original username but is unable to do so. A message turns out like this:

Sorry, this username has been disallowed.

Is it possible to change my username back to the original one? If possible, how do I do that? Thanks in advance.

are you trying to change it back to admin?

No, I'm trying to change my username back to another username which I used right after changing from the Admin username. My username after the admin username was bluebells, but I've accidentally changed it to another username. Now I can't change it back to bluebells. Is it possible to change back my username? If so, how do I do that? Thanks in advance.

Hi Bluebell You can change your name at any time by going into Your profile in the admin panel, modifing it directly, and clicking save. That should update it for you. I'm not sure why your getting that message.