Install app on just one erpnext instance

I have made a custom app. What my question is. For ease of setting up everything I am only using 2 domains(two different types of businesses) and have had multiple sub domains for each individual business.

I want only one subdomain to have access to this app and no one else. How do I do that cause it is popping up in the install apps folder. It does not really matter but it bugs me. Or an itch that has to be scratched