The two collaborated on the pop hit and the video was released on May 22, but there was a small incident while rehearsing the dancing for the short film when Gaga, 34, accidentally scratched the eye of her fellow pop princess Ariana Grande, 27.
"I shanked her with my nail by accident [while] dancing," Gaga said in the video.
The clip then cut to a shot of Grande lying on the floor looking at her phone as someone asked her what had happened.
"Lady Gaga scratched my eye," she said with a smile. "It's an honor I hope it scars."
Gaga then asks for some Neosporin to treat the scratch.
Later in the video, Gaga and Grande wrestled as Gaga attempted to put ointment on the wound.
"I want it to stay," the "thank u, next" singer insisted before running away.
"You have a scratch on your face," said Gaga, chasing after the star. "You can't get infected before the video."
The Instagram video also gave fans a look into Gaga's acting process for the video.
"You know what would be great? Right before you yell 'action,' maybe just be like 'what was the song about?'" she told a crew member. "I won't answer you, just be like, 'why did you write it?' and then yell 'action' right before I go ..."
She also offered commentary on her costume: "I've got a frontal and a back wedgie, I'm freezing and my makeup's flying off my face no matter how much glue we put on it."
The scratch may have been worth it, however, as the video and song received seven nominations for MTV Video Music Awards.
"Rain On Me" is up for video of the year, song of the year, best collaboration, best pop, best cinematography, best visual effects and best choreography.