Based on the context and the answer, generate a question. 

Context: Rin heard nothing intelligible , as if words had already fled far beyond his reach . He let out a slight grunt , then a louder one . His attention turned inward ; his eye dilated and his brow creased . Thrusting his hand further under his clothing , he seemed to search around in the area of his groin - surely he had n't lost track of that ?

Answer:

He was in a tremendous amount of pain .



What may be the reason he let out a loud grunt .