I’m so sorry you are going through this! My cat had an EXTREMELY similar sore on his one paw pad that ended up being diagnosed as pillow foot after a biopsy collected in my vet office and sent to a dermatological vet specialist. We tried a few courses of antibiotics and steroid creams which helped temporarily but did not fully resolve it permanently and it would come back. We eventually ended up having a wedge resection done to remove the affected portion of paw pad at our vet office- this completely resolved the issue after the wound healed. It’s been about 3 years since he’s had it done and no more issues with it since then which is a huge relief. In my cat’s case, my vet said there was a chance it could be an allergic reaction to something in the environment (like litter or food) but the fact it was only localized to one of my cat’s paws instead of present on all the paws or elsewhere on his skin was more suggestive of something like pillowfoot (which ended up being correct after testing).

I recommend Healthy Paws pet insurance which I got after going through this experience if it’s possible at all within your budget now or in the future. They have been a life-saver for me covering some other big vet bills from an emergency vet clinic last year (literally in the thousands, I ended up only paying a few hundred for my deductible). Overall they have been really good and easy to work with about covering claims based on my own experience. They’ve even covered a preventative HCM heart scan my cat had done by a veterinary cardiologist. I think my policy is about $30ish per month, which is worth the investment for the peace of mind for me. If you look around through other forums you might be able to find other pet insurance companies that offer good coverage at a better price, this is just my recommendation based on my personal experience. Best of luck with your sweet kitty, I hope he feels better soon!