My engine light is on and blinks when i get on the throttle/drive agressively.
I scanned it and get this "P0327 knock sensor 1 circuit low bank(1)". What does it mean?

 

It literally means there is a problem with the knock sensor or the related wiring. If your SES light is blinking that's bad...I know when it is a misfire code, a flashing SES light means you risk damaging the catalytic converter(s).

 

Is it an expensive fix?

 

Likely the electrical component, for less then $100 at your local auto parts store.