it's very hard to heal this sort of thing. The problem is it's an open wound in a wet not too clean place - infection is often the norm not the exception and they tend to get bigger if not dealt with. Sometimes packing it will help to promote healing, but that is dependent on size.

Your surgeon will likely suggest surgery of some sort.

I'm also going to suggest asking about HBO treatments to try and heal the area, and diet.

I know it sounds weird. (not the HBO - the diet part) but you have two issues at this point. 1) infection 2) poor healing - and both can be related to a weakened immune system.

Don't forget your body has spent some serious energy fighting cancer, and then healing from your surgeries.

I'm not suggesting hocus pokus or anything. Just take a good strong look at your diet, is it high in sugar and processed foods?
Try taking a daily vitamin, upping your protein (using a NON animal based protein - eat meat if that's the norm for you but if you are adding more protein try doing it through legumes, veggies, and beans). This gives you a well rounded diet and is actually good for you. I guess what I'm saying is eat healthfully - fresh foods, lots of veggies, minimize processed, sugar and chemical laden foods. Walk or do deep breathing exercises to help increase O2 intake. I will help you feel better and boost your immune system.

If you are already a super healthy eater try adding more greens etc...

Finally if HBO is not possible, then try brushing your teeth after every meal, and rinsing. keeping the area clean will help minimize the infections ability to spread.

Hugs.