The Curse of Frankenstein

Baron Frankenstein: Pass the marmalade Elizabeth.

Baron Frankenstein: I've harmed nobody, just robbed a few graves.

Baron Frankenstein: Let's let our friend here rest in peace... while he can.

Question: After showing Paul that he revived the creature, Victor attempts to prevent him from going to the authorities. While doing so, he gets flung against a support beam, and he clenches his upper right side in pain. What did he injure himself on?