Where is the tattoo shop in Nordhaven?

There isn’t a separate tattoo shop build, but you could download one that simmers have created from the gallery and place it in your game. Also the Sarpong family in the game run a tattoo shop in their home that your sims can visit.

Ok thanks. I'll just send my sims there then. If I place a tattoo shop from the gallery how would I go about making it an npc run business? I've heard that these businesses don't work like the old ones in Get To Work.

I am not quite sure but what EmmaVane posted in this post may help 
Q&A: Businesses & Hobbies | EA Forums - 11938444