A blast of green light blazed through Harry’s eyelids, and he heard something heavy fall to the ground beside him; the pain in his scar reached such a pitch that he retched, and then it diminished; terrified of what he was about to see, he opened his stinging eyes.
There are no more uses of "retch" in the book.
Show samples from other sources
The smell made me retch.
Then I grew sick, and retched to vomit, but could not, for I had nothing in my stomach to bring up.
Daniel Defoe -- The Further Adventures of Robinson Crusoe