How to soothe & heal cats open wounds?

My cat is 16 years old, he was diagnosed with diabetes about 7 years ago, and just recently around June of 2022,the vet found a mast in his neck, it moved to the opposite side of his lower jaw within days, after getting a biospy, the vet found some spindle cell and some benign fibro plasia but said the test inconclusive.. Since then, the mast(tumor) on his lower jaw has increased significantly in size, at least triple the size..   But he's scratching himself pretty bad, on the tumor, and on his face and neck all around the tumor, because I bet it feels weird on his face since it's huge and he doesn't know what it is and doesn't know any better. Tonight, he scratched himself completely open, it's raw, bleeding, wet and looks very painful.. What can I put on these wounds to make them less painful/sore and help them heal faster? Neosporin? Vaseline? Triple antibiotics ointment? Hydrocortisone cream? Calamine Lotion? Coconut oil?

Hello.  It sounds as though your cat has a probable mast cell tumour that has been scratched to the extent that it has split open, is bleeding and at risk of infection (because nearly all cat-claws carry bacteria and nearly all cat-scratch wounds are infected.  I say 'nearly' because there's a possibility that there might be an exception somewhere, not because I've ever seen one.  Diabetes potentially makes the infection risk even higher, too).  I wonder why you are asking me, and not your own vet?  Is the threat of euthanasia looming on the horizon?  Upsettingly, a large sore that is open but continually being played with, suggests a lot of discomfort on the patient's part.  Furthermore, if this is a mast-cell tumour and the cat is continuing to scratch, then healing is likely to be difficult and not necessarily helped very much by applying shop-bought products.  Please do see your vet - or another vet - because it sounds as though a full assessment of the case is what is needed.  There are chemotherapy options available now for Mast Cell Tumours, but they may not help so late in the day.  It sounds as though you need to know what a realistic future for your cat looks like, what options are available to you and some help to make a decision from there.

Because your cat is likely scratching as we speak and sounds uncomfortable, and the skin may be likely to get worse before you see a vet for an appointment, an emergency phone-call for triage / assessment may be a good way forwards.