Can a hit to the kidney area cause diabetic nephropathy to accelerate?

Not blunt trauma. A physical hit to the kidney, such as during contact sports should not worsen kidney disease due to diabetes. Diabetic nephropathy is accelerated most frequently by poor diabetes control and uncontrolled hypertension.
No. Diabetic nephropathy per se is related to hyperfiltration in the kidney thru a complex mechanism. A hit to the kidney could conceivably cause kidney damage from other reasons but it wont accelerate dm nephropathy.