Do I need to wait for my business registration before I start building and selling?

No. You do not have to wait to get up and running. Most of what you do to launch, such as creating social media accounts, posting and getting your site online, does not depend on your business registration.

The main thing that may need the registration is setting up your Stripe account under your business, and it is fine to wait for that. In the meantime, do what you need to do to get the sale, even if a customer has to mail you a check or you use PayPal. Keep using the platform, stay in the community and keep building.