If you permanently deleted the second Nintendo Network ID (NNID), then there isn't a way for you to change the email address now, sorry.
So probably the best thing to do is give a call to Nintendo's 1-800-255-3700 (6 am ~ 7 pm Pacific, everyday) Customer Service number, or use their webform to contact them, and one of the service representatives should be able to connect it with your first NNID.