Feedback resistors not connected to boost regulator
Is there any chance that if feedback resistor is not added, the IC can
  get damaged?


Yes, it's quite possibly damaged: -



The absolute limit of voltage difference between the incoming supply and OUTN is 24 volts so, if your incoming supply was 5 volts and you saw -30 volts at the neg output (possibly -30.5 volts at OUTN), that's a total difference of 35 volts and significantly greater than the allowed 24 volts.