PA and NJ have tax reciprocity for W-2 wages and salary. That means that NJ residents who are employed in PA are not subject to PA state income tax on their pay. Their work income is taxable only by their home state of NJ. Ideally, your PA employer would withhold NJ income tax from your pay. If they do not withhold NJ income tax for you, then you must make quarterly estimated tax payments to NJ. You can find the details on that here:
https://www.nj.gov/treasury/taxation/njit20.shtml
I would also recommend that you file PA Form REV-419 with your employer, in order to document your NJ residency. Here's a link to that form:
https://www.revenue.pa.gov/FormsandPublications/FormsforBusinesses/EmployerWithholding/Documents/rev-419.pdf