Ouch! When else have I given dodgy advice.
I wouldn't worry mate.
I wouldn't dream of suggesting that you should drive with a nail in a tyre, even if it is to a tyre dealer. What would happen if the tyre decided to go flat on the way there? At best you will need to get the tyre changed, at worst you could have an accident.
You are better off pulling the nail out yourself, if the tyre goes flat then take the tyre to be fixed in the boot of another car, or use the spare. If the tyre stays up, then I can understand the argument that the tyre may be weakened, but you probably run over loads of things on the road, if they don't puncture the tyre or get stuck in you wouldn't even know about them.
About 12 months ago we got a new van at work. I was driving it and had a puncture on the A34. That turned out to be a nail, I managed to get the van stopped safely but I ended up blocking one lane of the dual carriageway until someone could help me change the wheel. There was no way I was going to change the wheel in the middle of the dual carriageway so the AA were called.
Anyway, when I got back I was told that the nail was in there before I left, and it had been left in so that the tyre would stay up.
I do generally look around a vehicle before I drive it, but I missed the nail.