He might find himself in strange situations that the fanfiction writer has created. For example, he could be stuck in an alternate dimension where the rules of his powers are different. Maybe he's trapped in a world where all his friends have turned against him because of a plot twist in the fanfic.
Peter could get a dog. A loyal dog would be a great companion for him, following him around during his daily life and even being a sort of sidekick. It could sense danger and bark to alert Peter when something was wrong.
One idea could be that Peter Parker gets a prosthetic after a particularly dangerous battle with a villain. Maybe his leg is severely injured and he has to adapt to the new prosthetic while still maintaining his superhero duties. He could struggle at first with the balance and movement, but with his determination, he eventually masters it and even modifies the prosthetic to have some special features like enhanced jumping ability.
He might first use his spider - sense to try and sense any danger or clues about how to get out. His super - strength could also be useful if he needs to break through any physical barriers in the fanfiction world.
It could be a vengeful criminal that Spider - Man has put away in the past. This criminal has spent years in prison plotting his revenge and finally gets the chance when Peter is vulnerable. Maybe he manages to ambush Peter in an alleyway while he's on his way home from school or work.
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.
His personality might become more in touch with his emotions. As a girl, Peter could be more empathetic and sensitive. He might also be more cautious in some situations, as society often treats girls differently. For example, he might not be as quick to jump into a fight without thinking about the consequences more carefully.
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.
In such a fanfiction, Peter might lose his usual control. He could accidentally reveal his identity while drunk. For example, he might start talking about his Spider - Man adventures without realizing it.
It could be some random students at Peter's school. Maybe there are those who are jealous of Peter's achievements in science or his closeness to his friends like MJ and Ned. They might start bullying him just to make themselves feel better or to fit in with a certain clique.