Confused between PhD and state assistant professor exam

I have upcoming state assistant professor exam for which I have cleared SET. And I today I have recieved PhD offer letter from IIT Ropar.
As for the state exam I have to study state gk history and other stuff as well along with my subject knowledge (physics). So I am confused that should I join PhD or prepare for my state exam and then later try for physics. I already took a drop year after my MSc in physics. Please help me.