Now I say this not so you can sit back and let others do the hard work, but for you to figure out how else you can contribute. Every startup, hell every mature company, has issues to deal with on a daily basis. I would be very surprised if there wasn't something else you could be doing for the company.
Worst comes to worst, your job from here on out is to do the tasks nobody else wants to do. From a technical perspective that could mean things like sanitizing the database (if it needs it) or going back and writing some good tests for already-implemented code. From a business perspective, this could mean researching, scraping, generating leads to customers, users, etc. Hell, you can even be the glorified secretary by helping others manage their day-to-day tasks, schedules, appointments. Be the office janitor. Be the guy they send to campus events to talk to students.
If you can no longer contribute to the code for your product, that's OK. There's a million and one things you can do outside that realm to support the product as well as your teammates.
Of course you can always buckle down on your coding game and get better at it. Take online courses. If you (and your company) can afford the time and money, go to one of those schools that teach you to be a better programmer. Tell your CTO that you want to get better and want to learn from him/her.
Be the glue that holds everyone together. Be the swing man that can bounce from activity to activity and ensure everything is running smoothly. Be the founder who's relentlessly resourceful and continues to move the company forward in any shape or form.