I'm not quite sure what you are asking, but will try to respond.
There is a large muscle called the piriformis that attaches by the sacroiliac joint and runs across the buttock area to the hip area. It is one of the major muscles that aiRAB in hip rotation and is important to walking. It can get irritated from an injury such as a fall; it can also get irritated from sitting too long, etc. In most people the sciatic nerve runs beneath the piriformis, but in a small percentage of the population, the sciatic nerve is actually kind of intertwined within the muscle.
There is a syndrome that has symptoms similar to sciatica called "piriformis syndrome." Sometimes doctors have a difficult time telling if the patient's leg or hip or groin pain is originating in a spinal nerve root, caused by something like a herniated disc or stenosis, or if it is caused by a taut piriformis muscle.
In any case, if there is any swelling of the piriformis, as there is bound to be if you fell, it often causes irritation of the sciatic nerve, resulting in what we typically think of as "sciatic pain."
Nerves, including the sciatic nerve, can get very angry when irritated...and they can take a VERY long time to recover. I know from personal experience that once the piriformis becomes inflamed, it can be difficult to get the whole thing to calm back down.
I suspect it was this sort of scenario that your doctor was describing when he talked about the sciatic nerve being damaged.