My foot pain is in the instep of my left foot, about 1/2 way between heel and big toe. It hurts to touch it. It hurts after a long day on my feet, but the worst pain is when I am laying down. It either feels like a flowing, burning pain, or stabbing. Does not hurt continuously. Anyone with a guess?

No guess. There are just so many nerves that can be pinched, irritated, or have something pressing on them, from your torso on down. Pain often 'refers' from other nerves further up, even above the knee, or from the abdomen.
I know because I had pain for almost 40 years that started from the sacral nerve on the back, on the sacro-iliac, but none of the pain was in my back. It took forever to get it diagnosed - by a chiorpractor.
If I were you I would see a podiatrist if there isn't a sports clinic near you.
The fact that it hurts lying down is a possible clue to something up around your lower abdomen or hip.
You could have some sort of stress fracture of a foot bone from standing all day.
I fell once, hurt my ankle, which was brutally painful until I pressed on the side of it one day and a huge bruise instantly came to the surface. The pain stopped instantly, because the blood was no longer pressing on a nerve deeper inside.
So many things it could be...