There is no rights based administration system in Openfire. So only full admin (or admins) can add users. Your admin can add your username to a /conf/openfire.xml in correct place, so you will be able to login to Admin Console. The only solution i can think of. There is also User Service plugin. With its help one can send http requests to a server (to add/del users etc.). This will need some additional work (to create an application to use that requests, etc.).
The Helga-Bot plugin has advanced features to control shared groups. Maybe that is what you are searching for:
Invite the (local) user “someone@yourserver.com” to your group “woc” would be done by a chat message to the bot like this:
group invite -g woc -u someone
user “someone” gets a message from helga:
You have been invited into group 'woc' by admin@yourserver.com. To accept this invitation, just answer with the command 'group join -g "woc"' on this message.
The user need just to copy&paste the command.
Because everything is done by this chat messages, every jabber client should support it.