Have Cat Questions? Ask a Cat Vet Online.
Hi. My name is***** Thank you for your question. When dog or cat suddenly has a swollen tip of the ear pinna and it feels fluid like, the most suspicious situation is an ear hematoma. They can break a blood vessel in the ear cartilage and it will bleed and form that blood pocket in the ear. With a lot of cats, this happens because they are scratching their ears due to either ear mites or an underlying ear infection. The best thing that can be done is to get him to your vet as soon as you can for them to look at the swelling to confirm this. Then can then attempt to drain it and then treat any underlying ear issues that caused this to happen.
Here is a very good link on it.