BuddyPress.org

When you will use that above link to create user then it is giving you a user_id in return then you can use it to save profile data like this:

xprofile_set_field_data('profile_field', $user_id , 'profile_field_value');

You can write it just after the code where you get user_id in return.

Also please use hook ‘init’ in place of ‘admin_init’ and check a condition in the function if form is posted.

Please try this once and let us know if this works for you not.

Thanks