There is no issue in selling to unregistered person.
If you buy from unregistered person then RCM becomes applicable. Otherwise there is no problem in selling to unregistered person.
I think many people are confused over dealing with unregistered person.
There is no problem in selling goods to unregistered person. You do not have to shut the shop. continue your business in same manner as you are doing. Just the bill format will change and tax rate will change.