Q. Will I have to pay 2 state tax?
A. Technically, yes, but "nobody" does. See http://money.cnn.com/2013/06/28/pf/taxes/business-traveler-tax-threat/ If you live in a state without an income tax (e.g. FL or TX), it’s more likely you should file in the work states. You can't use the "it all comes out even" rationale for not filing.
The general rule is: your report all your income on your home state return, even the income earned out of state. You file a non-resident state return for the state you worked in and pay tax to that state. Your home state will give you a credit, or partial credit, for what you paid the non-resident state. You will have to file a non resident NJ state return and pay NJ tax on the income earned there.. You will also file a full year resident return, for your home state, and calculate tax on ALL your income. Your home state will give you a credit, or partial credit, for the tax you pay NJ. So, there will be little or no double taxation. But you will have the cost and hassle of filing two state returns. Do the nonresident state return first.
NJ, like most states has a total income filing requirement. That is, the requirement to file, is not based on just the income you earned there. See https://www.state.nj.us/treasury/taxation/njit24.shtml