I also started on a very small company. Worked there as Junior developer for about 3 years. I was on the same spot as you are right now. One day, I received a call from a friend who started working on a bigger company in a different state (I live in Brazil), saying they were hiring. I figured I could at least try their technical tests to see where should I improve.

So I applied for the junior position. They thought my test solution was good, so I got to the interview phase. To my surprise, the interview was not for the junior position, but for the medior one (don't know the correct term, but higher than junior but lower than senior), and receive the job proposal on the next week.

I agree with @MagicShel@programming.dev's comment: "you need exposure to other environments, other ideas, other technologies and frameworks in order to grow". And it goes both ways. Without testing yourself, you'll never know how much you did grow and where you are.

So, my advice to you is: do not wait until you feel "ready" to do the move. It may "click" too late. If you want to move on, just do it. At least you will test yourself, and know how to correct your course, if you need to aim higher ou lower than originally intended.