There should be no grinding noise... ever
. Can you tell where it's coming from?
If the rear wheel very possible the brakes/brake pad needs adjustment. The pad is held in place with a magnet and if it ships loose, it may have come unseated. if this is the case it just needs to get opened up and re-set.
If coming from the front wheel (but not he motor), say if it's clicking - it may be the air pressure valve hitting the fork on each rotation. The clearance there is super tight so if it's hanging a little far it can definitely hit. Just tighten the lid OR deflate the tire enough so you can push the whole nozzle back into the wheel (slightly) and then re-inflate.
If the sound is coming from inside the motor itself - stop riding immediately and get it returned. That may indicate a loose magnet which will self-destruct at some point.