You can stick caltrops in dung so they are more dangerous than "3cm nail in the foot" would ordinarily be. For actual handheld weapons, keeping them in good, sharp condition is kind of a priority, since it's small comfort to know the dude you scratched had a bad time a week after he partitioned your ass like it's Poland. Of course peasant armies often went to war with whatever pokey tool they had, and you can absolutely get tetanus from getting stabbed by a hay fork or a straightened scythe. Against armored opponents, sharp weapons are of little use, so knight vs knight combat would have been maces and hammers mostly, and those don't do deep stab wounds anyway (except war picks and morning stars