iPhone XR camera issue

Try taking a picture where the entire photo is darker (no bright lights or bright areas in it) and see if that "noise" is in the entire frame. Mobile Phones have relatively small sensors (compared to regular digital cameras) and getting noise in dark/dim areas is not unusual. So by taking a picture where the entire frame is dark/dim will let you know if the issue is the sensor/lens itself or just noise in dark areas.

Have a close look at the lens to see if there is an oily residue on the lens surface multi-coating. If so, clean it with a micro-fibre lens cloth. But first remove any particles and lint by carefully blowing or dusting them off. Then, before wiping with the micro-fibre cloth, first breathe on the lens surface to create condensation to aid in cleaning and removing any oily residue.

Regards,

Brian