You must file a non-resident NJ return if you have NJ-source income and your gross income from everywhere for the entire year is more than $10,000 if filing Single or MFS, or $20,000 if filing MFJ or HOH. NJ will tax only your NJ-source income.
https://www.state.nj.us/treasury/taxation/pdf/current/1040nri.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.