Our Dog Has Been Biting His Paws And The They

Our dog has been biting his paws and the they are now raw spots. Today, he is not himself, as he just wants to lie down in one place. He is normally very active. He's 2-1/2 year old lab and is in the house. Our vet office is closed today. Do you have any ideas of what could be wrong with him? I really appreciate your help. Thank you