He's almost ten but one fell out today and he has a little hole where it used to be. Will it just heal naturally or should I take him to a vet? he is eating fine and was purring a little while ago so I don't want to waste money on vet fees if I don't have to.

I'm not an expert but if I was you I wouldn't take him to the vet. An elderly cat having a tooth fall out is probably quite normal. I'd just keep an eye on him make sure an abcess doesn't develop or something like that. If he doesn't seem concerned and is eating and seems happy why stress him out dragging him to the vets?

Purring doesn't always mean they are happy but hopefully you can see if he's miserable.
Only my opinion - others may know better. Over the years my beast broke or had extracted a fair number of teeth, it never stopped him in his tracks however few he had left. One time he came back from the vets having had 4 removed under general anaesthetic and he tucked straight in to some crunchy food the minute he got through the door.
What I'm trying to say is that cats are incredibly resilient and your cat will likely be fine if you do nothing but do keep an eye out for any sign of him having trouble eating as they can be in quite a lot of pain without showing it.

Thanx for the replies I will keep an eye on it.