You could use pliers, you could very carefully hit the corners of the head in a clockwise direction with a hammer, you could spend a lot of time training the strength in your hand and arm to tighten it by hand, you could use a dremel, saw, or file to cut a slot into it and tighten it with a screwdriver
Is it easier or harder to tighten a bolt without a wrench?
It’s neither, it’s impossible
You could use pliers, you could very carefully hit the corners of the head in a clockwise direction with a hammer, you could spend a lot of time training the strength in your hand and arm to tighten it by hand, you could use a dremel, saw, or file to cut a slot into it and tighten it with a screwdriver
But it’s a lot easier to use a wrench.
NUH UH IT’S IMPOSSIBLE
(/s)
That’s not repairing it, that’s just breaking it further.