After changing my oil recently the oil pressure light came on and I would hear some clunking noises coming from the engine bay. As soon as the light comes on (takes a couple of seconds) I turn the car off and after starting again it doesn't come on and everything seems fine. One thing that also happens is the RPM drops immeditly to about 800 even after a cold start and I am used to it staying up there for a minute or two although I am not sure if that's related. The car is a 2015 B7 Passat with the 1.8L turbo engine. While changing my filter a couple months ago there is the piece that broke off the hub (second picture) but I am not sure if that is also related to the oil pressure light or not as the car has been running fine for a couple of months with it like that.
So what would cause the light to come on after doing the oil change?