Poisonous isn't the right word; they're infectious (because the best a cat can do to clean its claws is lick them and they literally use their paws as shovels in their little poop boxes)
For the record cat claws can be very infectious, especially if they've just used the sandbox. The poison thing is not a joke. Please be careful when handling cats.
It would be minor swelling, but if you treat it immediately it will heal. I immediately treat with Hydrogen Peroxide and Iodine Tincture so the wound dries up.