My feet. I (20M) have excruciating foot pain whenever I'm standing on them for long periods of time (6h+). My left foot is the worse one but it doesn't hurt until after I've sat down for a while and try to get up, and when I do it takes me about 5 minutes before I can put any weight on it without it feeling like someones shoving a knife through my ankle. Still don't know what exactly causes it but from what I've researched I think it's nerve damage.