Really, try and relax, it's not terminal, it may even clear up by itself after a good long run. You won't do any damage, just drive it.

Again, I second that.

I've seen tappets that have been destroyed and still being used.

It will have poor mpg, smoke, down on performance and sound awful when it's completely failed.

Short journeys won't make a difference. It's never good for a diesel to start with but In this situation it ain't going to make or break the car.