I have been in the same position - not really a scrum master role but I was working at an agency where I was rapidly promoted from entry level to team lead and then to front end architect in a span of 2.5 years. I was a total noob when I joined but I just happened to be able to give a false sense of advanced knowledge to my managers because I did a couple of Lynda/Pluralsight/Udemy courses. Very soon I was knee deep in doing advanced config/work flow setup/ridiculous guesstimation for full blown ecommerce projects!!.
In my team lead/architect role I had to take responsibility of a team of 3 - 4 devs who were all more experienced (in years of experience) but simply lacked architectural/workflow/JS knowledge because they had not bothered to learn more. But anxiety + responsibility of managing team, providing estimates, planning tasks, assigning work and just doing my job scared the crap out of me every day because deep down I knew that if a real front end architect reviewed my work I would be exposed as a fraud. Because there was no formal code review process - my managers thought that I could do it all and do it perfectly - which was very far from the truth.
What kept me going? 2 quotes that I kept repeating to myself every day as I started my work or when I was afraid that I was going to crash:
Never let the future disturb you. You will meet it, if you have to, with the same weapons of reason which today arm you against the present.
Just keep swimming
Even though I eventually quit that job due to lack of learning opportunities, I am glad I did it. I don’t know if I did it well or poorly but I delivered and it taught me a lot about architecture, best practices, leadership and led me to stoicism - which has helped me to greatly deal with obstacles and anxiety. I hope it might help you too - https://www.goodreads.com/book/show/18668059-the-obstacle-is-the-way