DUHHHHHHHHH, I'LL BUILD A BIG WALL AND THEN FIGHT THOUSANDS OF MONSTERS WITH A SINGLE SWORD DUHHHHHH.
This MC is the dumbest mother fucker, why didn't he spend some time setting up the simplest measure of traps like shallow covered ditches with sharped poles inside them, they don't even have to be deep less than a foot will do, that way you can dig them long, make several rows of them and then create more walls funneling the enemies into a line, that way you get a good amount of them bleeding to death and then you can at least fight some in small groups giving yourself a chance.
Or how about some bombs? though I don't know if his world has the technology for them or not, if not then burning oil is always a good second choice, have some villagers dump it onto the monsters from behind the wall. Or if you absolutely don't want to let them know then spread it out around the village perimeter and light it after the monsters come, they'll be hundreds of them set on fire pretty quickly.
I really dislike this MC, he's had like 15 years to plan for what he's going to do to save his village and everyone he loves and his carefully laid out plan consists of building a fucking wall and then charging out there with a single sword, he doesn't even have a back up for when he inevitably loses it or breaks it on a monster. Also what the fuck, he's injured within seconds of starting the fight, he's just the worst.