A couple of days ago, I was playing with Zoey's paw and felt a little bump on the underside of her paw under her first and second "toes". When I looked at it it kinda looked like a small blister. I put some ointment on it but didn't think to much of it since she wasn't limping nor did it seem to cause her any pain. I just looked at it this morning and it was a lot bigger. She still is not limping but she didn't like me touching it. Any suggestions? Should I just keep an eye on it or take her to the vet?