After Stress Relieving we found a 1" nozzle(pressure gauge) is distorted, is there any local rectification permitted as per the code? what precautions can we make to avoid distortion?

NPS 1 nozzle couldn't be distorted by its weight, but somo superimposed weight which should have been avoided to happen. It can be straightened cold or, if for that material and thickness, PWHT was not mandatory, by hot working.
When possibility of distortion due to its weight exist (big dia and weight associated to small thk.), the item shall be better supported by adding temporary supports. Supports, and temporarily added supports shall be calculated by the Tec.Mgr.
Mauro