I am assume that this defect has actually healed in and is not an open wound. After all the things that have been done to me I have several similar places in my mouth and back of my throat. Food gets caught in them routinely. For me though it is a simple process of after meals, gargling with water over the sink to remove all this stuff. It's a pain when I am out at functions, but most of the time it is only a small inconvenience. But these defects never return to normal contours. I wouldn't consider a surgical procedure to fill in the defects with something, if they go all the way done to boney structure this could be done with hydroxlapitite particles, which is used both by itself or with autogenous bone graft material and then the tissue laid down over the top to heal. HA has been used for some time to repair boney defects.
If this is after the infection, now some kind of open wound, this is another kind of problem. Radiation does make it harder for tissues to heal, in some cases require 02 therapies to get wound healing and closure.