I'm confident that many UX teams started from a team of one, and progressed through a similar growth process to become larger and more mature UX organizations. I hope that sharing my experience might help others in similar shoes to make their work, and UX maturity progress more efficient.
Do you work in an organization that doesn't have an established UX discipline, a clear owner of UX in the upper management and any shared design practices? If you do - you may have an excellent opportunity to advocate for Users and their needs and start the conversation about the User-centered design process. Bringing the UX process into a project is the first step in that direction.