The other hunters in the Supernatural world, like Bobby if he was still alive in the fanfic, would also be worried. They'd offer their expertise and resources to help Dean. Bobby might give Sam some advice on how to take care of Dean while he's unconscious and how to find the culprit.
Often, other characters might come to Dean's aid. Castiel could use his angelic powers to heal any internal injuries Dean might have sustained. There are fanfictions where Castiel hovers over Dean, his blue - eyed stare intense as he channels his grace to heal Dean's head injury from being knocked out.
His friends would be very concerned. Kanan, being his mentor, might feel responsible. He could use the Force to try and sense Ezra's condition. Chopper, on the other hand, would probably be buzzing around nervously, trying to help in his own mechanical way.
Dean would probably be extremely confused at first. He might stand there, staring at his car with a bewildered look on his face, muttering things like 'This can't be real'.
Dean would probably be very protective. He's always been the big brother looking out for Sam, and with Sam as a kid, that instinct would be even stronger. He'd be constantly worried about Sam getting hurt and would keep him close at all times.
Stiles might be initially shocked. He would probably feel betrayed since he thought of the pack as his family. He could go into a state of denial at first, not believing that they would actually kick him out.
Some characters might be very worried and rush to his aid. Others could see it as an opportunity to gain power or influence in his absence.
Kagome usually gets very worried. She'll immediately try to use her spiritual powers to heal him if she can. If not, she'll search for herbs or other ways to help. Miroku would likely offer his support in a more practical way, like finding a safe place for Inuyasha to rest. Sango might be on guard, making sure that no more enemies take advantage of Inuyasha's weakened state.
Some characters might be shocked. They could never have expected Dexter to be involved in such situations.
Harry would probably be extremely worried. He'd immediately rush to her side, trying to figure out how to help. Ron, on the other hand, might be in a bit of a panic at first but then would do whatever he could to protect her while waiting for help. Hagrid might bring some of his home - made remedies, thinking they could work on her injury.
I'm not sure specifically about 'dean squirting' fanfiction as it might be a rather niche or even inappropriate concept. However, there are many great Supernatural fanfictions in general on platforms like Archive of Our Own. You can search for Dean - centered stories there and find some high - quality ones that are more in line with the general themes of the show.