Our 3 year old staffie dog is having problems with his claws they are splitting from the bottom half?

his dew claw has split today this makes 3 in total now over the past couple of weeks the first split was very painfull for him i took advice from the vet who said to put a sock on till it healed , all of his claws look as if they could split the top half looks ok but the underneath seems soft , im concerned now any advice would be greatly appreciated .