Thank you for contacting Petco Pet Education Center, formerly Petcoach with your question about Clover. Poor girl! This could be caused by an injury, an infection (fungal or bacterial), allergies, or a nutritional deficiency. She should see her vet for this problem to diagnose what is causing it, but it's not an emergency so you can wait until tomorrow. Clean the paw pad, and examine it closely to see if there is any foreign material in it. When you clean it, use warm water and an antibacterial soap. Apply a bandage, and make sure it's not too tight. Put a sock over her foot and bandage to protect the bandage and to keep her from chewing at it. You can secure the sock to her leg with some medical tape. Keep the area clean and dry, and take her into the vet tomorrow. Best of luck.