There might be a lot of such fanfictions out there. However, to find them, you need to use effective search terms. Maybe adding the name of the source material (if it's based on a particular movie, book, etc.) to 'Peter gives himself stitches fanfiction' in the search bar would help. For example, if it's related to a superhero story, adding the superhero's name.
I'm not sure specifically as there could be many different interpretations of such a fanfiction. It might be about Harry in a situation where he has to give himself stitches, perhaps after getting injured in a dangerous adventure, like a battle in the wizarding world.
Obviously, Harry would be the main character. But there could also be other characters involved in the events leading up to him having to give himself stitches. For example, his friends like Ron and Hermione might have been there before and left him in a situation where he got injured.
Another theme could be pain and endurance. Stitching oneself is a painful process, so the fanfiction might explore how Peter endures this pain and what it says about his character. It could also show his determination to keep going despite the injury. Usually, in these stories, there's also a sense of secrecy or isolation, as he might be stitching himself up alone, away from others for some reason.
One good 'Peter stitches himself' fanfiction might be found on popular fanfiction platforms like Archive of Our Own. You can search using relevant tags such as 'Peter' and'stitches' to narrow down the results.
The 'Peter Parker Gets Stitches' fanfiction might be centered around the idea of vulnerability. Peter is often seen as a strong superhero, but getting stitches shows his human side. It could be about how he copes with this moment of weakness. There could be a lot of internal monologue as he sits in the hospital or wherever he gets the stitches, thinking about his responsibilities and how this injury might impact his future as Spider - Man.
Peter Parker is the main character for sure. In addition to Aunt May and MJ, there could be other characters from the Spider - Man universe. For example, Doctor Strange could make an appearance if the injury has some sort of magical or other - worldly aspect to it. Or perhaps Iron Man's influence could be felt if the story is set in a universe where they have interacted. And let's not forget the Daily Bugle crew, like J. Jonah Jameson, who might be looking for a story about Spider - Man's injury.
Well, it's quite possible. Fanfiction is known for its creativity and bending of established norms. This particular idea of Tony giving birth to Peter might be someone's wild and creative take on the relationship between these characters. It may not be a common or mainstream concept, but in the realm of fanfiction, where the sky's the limit, it could very well exist. You should start by searching relevant tags on fanfiction platforms.