My cat has a small sore near his ear, what could it be?

If there’s some pus and the whole thing looks kind of dirty, the best thing you can do is to use a cotton ball with hydrogen peroxide and clean the area a few times a day. If the swelling gets any bigger than half a marble, you should have it looked by a vet ASAP. It can quickly turn into a life threatening infection since cats that get puncture wounds abscess much more quickly and severely than most other species because their skin heals too fast and traps bacteria deep in the wound. If there is a white spot that’s kind of under the skin and won’t wipe off and wriggles around a little it could be warble – a bot fly larva (maggot) under the skin. They can also cause an abscess and are dangerous to remove on your own.