Maybe Astrid is hurt while on a mission to explore a new area. Hiccup, being the caring friend he is, sets aside his own tasks to stay by her side. He could search for a rare herb to heal her wounds. As he does this, their relationship deepens as Astrid realizes how much Hiccup truly cares for her.
One possible fanfiction could be about how Hiccup and Astrid deal with the pregnancy. Hiccup might be overprotective, constantly worried about Astrid and the baby. Meanwhile, Astrid could be trying to keep up with her normal Viking duties while also preparing for motherhood. And the lemon element could be a symbol in the story, perhaps it's something Astrid craves during her pregnancy, leading to some humorous or heartwarming scenes between her and Hiccup as he tries to find the perfect lemon for her.
Astrid might initially be in shock. She could just stand there, frozen, unable to believe that Hiccup is really gone. Her eyes wide open and her body trembling as she tries to process what has just happened.
In the fanfiction, perhaps there's a moment when Hiccup gets injured while protecting the village. Astrid stays by his side day and night, taking care of him. She reads to him, makes him his favorite food, and in those quiet days, they realize how much they mean to each other. Their love deepens as they share these tender moments.
It develops gradually. At first, they might be just friends who respect each other's skills. But as they go on more adventures together, they start to notice little things about each other. For example, Hiccup notices how Astrid is always the first to volunteer for dangerous tasks because of her bravery. And Astrid sees how Hiccup's intelligence always gets them out of tough situations.
Their relationship might become more equal in some ways. As dragons, they are both facing a new and strange existence, so they have to rely on each other more. They might develop a new understanding of each other's strengths and weaknesses.
You could also check out Tumblr. There are often fanfic writers who post snippets or links to their works there. Look for tags related to How to Train Your Dragon (assuming Astrid and Hiccup are from that), and then narrow it down to the 'Astrid Hurt Hiccup' theme.
The theme of sacrifice can also be present. Maybe Astrid gets hurt while saving Hiccup, or Hiccup has to put himself in danger to rescue Astrid when she's in a hurt state. This can add a lot of drama and intensity to the fanfic.
Well, the story could start with Astrid realizing she's pregnant. Hiccup is initially shocked but then overjoyed. The lemon could be a gift from a far - off land that Astrid receives early in her pregnancy. As the pregnancy progresses, Astrid might have to deal with morning sickness and mood swings. Hiccup tries his best to keep her happy, using the lemon in different ways, like making lemonade or using its scent to soothe her. There could also be some conflict in the village about the new addition to their family, but Hiccup and Astrid stand strong against it.