You first need to enter to your original region eShop with an NNID, if you don"t have one create one (note that purchases will be tied to that NNID), after that you need to open your eShop without an NNID, you can inject a blank NNID to make it quickier, you can get an already blank file from here:
https://gbatemp.net/threads/tutorial-how-to-bypass-nnid-bans-miiverse-online-eshop-etc.417999/
After that when you try to connect to your original region eShop without the NNID you should get an error, that"s alright power off the console; after that you will be able to enter to the changed region eShop, only note that your original region eShop will stop working meanwhile, so if you want to use your original region eShop again you need to make the same process.