You can manage any discomfort by giving the cat feline pain killers, restricting its exercise, preventing licking and placing cold compresses
on the
lump. In severe cases, your vet may insert a needle into the swollen sac to remove some of the fluid and relieve some of the pressure and pain, however, this is seldom necessary, rarely works for long (the fluid often refills in time) and does run the risk of introducing bacteria into a sterile, protein-filled site and setting up an abscess.