Welocme to RabbitTalk, mrsdowney! :welcome:
I'm sorry you are faced with this in your first litter.
Is your rabbit a dwarf breed? If not, the little one would likely be a runt rather than a peanut. True peanuts are not viable. Runts (weak, undersized but normal kits) may or may not survive.
If this kit has not nursed since birth, I would be very surprised if it survived much longer. In your place, I would remove it and euthanize it. This may sound brutal, but I would place the kit on a hard surface and hit its head with a hammer. It is sure, effective and quick. Put a newspaper under it in case there is any bleeding. You could, of course, have a vet deal with it, but it would be no more humane and will hit your pocketbook hard.
I do realize that if you raise rabbits as pets rather than for meat, this action may be very difficult for you. It was difficult even for me the first time I had a kit that needed to be euthanized, and I have butchered many rabbits for meat. If you can't handle it, you can just let the kit go on its own. It likely won't be long now.
Dood, what method do you use to euthanize them? My method works for me, but it is a bit much for some people to handle.