You would have to file a nonresident New Jersey tax return for 2018 reporting 0 income for New Jersey so that you can get a full refund of the NJ taxes withheld.
NJ-1040NR STATE OF NEW JERSEY INCOME TAX NONRESIDENT RETURN (2018) - https://www.state.nj.us/treasury/taxation/pdf/other_forms/tgi-ee/2018/1040nr.pdf
Instructions - https://www.state.nj.us/treasury/taxation/pdf/other_forms/tgi-ee/2018/1040nri.pdf
