What you achieved is actually pretty impressive. Teaching yourself programming and build a product with traction and worth of investment. Use this at your advantage, the kind of developer that you want to hire first will respect that.

Hire a Senior full-stack developer and communicate very well that the state of the platform (and the code) is at "junior" level. Use this argument to motivate him, many developers like the challenge to set standards and lead technical decisions early on in a project.