If you didn't get a W2 as an employee but got a 1099NEC then you are an independent contractor for both federal and state. Independent contractor, self employed, freelance, side jobs, gig work, consulting, sub-contractors are all the same thing. You need to fill out Schedule C for self employment and pay self employment tax on it.
Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment. You pay 15.3% SE tax on 92.35% of your Net Profit (If it is greater than $400). The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare. So you get social security credit for it when you retire.
