Temp stay in another state for less than 6 months, do I need to report income to both states?

I moved to NJ from CA last March with an intention of staying for about a month due to family emergency, but ended up stayed there until late August and moved back to California.  I have been WFH since March until now. My boss was aware of my stay in NJ but I don't think the company was. During my stay in NJ I also got my larger portion of RSU of the year vested in April.   My AGI should be no more than $400K last year.

 

I couldn't think any negative because NJ seems charge less in state income. My concern is my employer might not be aware of the situation and don't know if that will affect the validity of such a return.

 

So should/do I need to report state income to NJ during my 'temp stay'?