Accepted Answer

If your veterinarian conducted a thorough examination, which I'm sure was done, your baby is likely suffering with a soft tissue injury. This can can result from a jump, for example, or another injury unbeknown to you. These generally respond with time although anti-inflammatories can speed up resolution and make for a more happy pet. If the condition is getting better as opposed to staying the same, then it is likely a soft tissue injury. The other consideration of note is that I'm assuming that your feline is indoor exclusivey. If not, then the only other concern I would have is whether there had been an encouter with another cat resulting in a bite. With such an event, the condition would gradually worsen resulting in a fever frequently and you would notice a swelling and pain when you feeel the entire limb. Also check the nails for tenderness as this could be a nailbed infection or inury