After flying, i placed a turned on p3a on roof of my car to detach propellers.
Dji go gave me the compass error message. I turned it off tight away. Should i recalibrate the drone or its fine?
Why take a chance. Only takes a minute to recalibrate.
Too many people think Compass Error means there is something wrong with the compass and that calibration will fix it.
When actually the compass is fine but it's advising it has detected a magnetic field problem that needs fixing (usually by moving to a safer location)
Your compass is in the bottom of the landing gear.
You put right on top of the steel carand it's telling you that it's got a problem because of the magnetic field generated by the car.
If you just take it 20 feet away from the car, the compass error would be gone and you can fly normally.
DO NOT recalibrate in an area close to large Iron or steel objects. You risk screwing up your Phantom's compass and possible losing your Phantom.
I'd suggest testing to get a better understanding.
Put your Phantom on the car again and power up - no need to have props on.
See the compass error.
Take the Phantom away from the car and put it on the ground - see - no compass error.
Read this thread to get an understanding of what compass calibration is and when to do it.
Compass Calibration, A Complete Primer | DJI Phantom Forum
Fly safer with understanding.