Dr. Onesi

Dr.Tail Vet

Firstly, it's important to monitor the lump closely. Given that your cat was vaccinated a week ago, one possibility is that this lump is a reaction to the injection, known as a vaccine granuloma. These are not uncommon and can arise several days to a week after vaccination. They are usually harmless and resolve on their own, but monitoring is key.
Another possibility is that the lump could be an abscess, which is a collection of pus that forms as a result of infection. This could occur if your cat had a small wound that got infected. Abscesses can feel warm to the touch and may become more painful over time.
A third possibility is that the lump could be a cyst or a benign growth, which are generally not urgent.

Keep the lump clean and monitor its size, shape, and color. If it changes rapidly, this is important information. And ensure that he does not have access to any irritants or allergens that could exacerbate skin issues, and maintain a clean environment.
If the lump begins to grow, change color, becomes hot, or if your cat starts to lick or bite at it excessively, these could be signs of infection or irritation.

I recommend keeping an eye on him for now because he's acting normal and it's possible that this will resolve over time. If he exhibits any of the symptoms below, you may want to take him to the vet to determine the exact cause and condition.

- The lump grows rapidly or changes dramatically in any way.
- Your cat shows signs of systemic illness, such as fever, lethargy, or loss of appetite.
- The lump becomes painful, hot, or begins to drain fluid.

If you have any additional questions, please don’t hesitate to come back to us! Thank you.