You can enter the income without the 1099NEC. As long as you report the same amount or more. And you know you need to enter the gross income? Not just what you made after expenses. You enter expenses separately.
I would just enter it as Other self employment income or as Cash or General income. You don't need to get a 1099NEC or 1099Misc or 1099K. Even if you did you can enter all your income as Cash. Only the total goes to schedule C.
How to enter income from Self Employment
https://ttlc.intuit.com/community/self-employed/help/how-do-i-report-income-from-self-employment/00/...
