I would file a return. You must have had some income from somewhere, or else how did you live and pay fees etc.?
As for the business, single member LLC, unless an election is made for some other form of business, does default to a Sch C, Sch F, Sch E...depending on the business. From your brief description, I would say Sch C.
There may be some startup expenses that need to be decided on how to expense them. Elect to expense them, capitalize them and amortize them, etc. Any elections need to be made in the first year.
See Publication 583, Starting a Business and Keeping Records
https://www.irs.gov/publications/p583#en_US_202012_publink1000253143
**Disclaimer: Effort has been made to offer correct information; but due to the discussion forum limitations, the poster disclaims any legal responsibility for the accuracy of the poster's response**
