Hi Sneha,
In CMC, We do not see an option for WEBI Customization at the user level. We can only right click on 'User Group' and select 'Customization' and then select the WEBI tool bars that we want the end user to see. This does not have the option to restrict at the user level as principal. Has option to do this only at the Group level.
Please advise if you think there is a way to do this :-)
Thank you
Suman