Hi, so i went on hikes with backpacks that weigh about 60 pounds or heavier. my toenails are now black. or there is just dried blood under them.

Subungual hematoma: It is probably a hematoma (bleeding) under the toe nail. Will resolve on its own or you can "drain" them. To drain them you can either heat up a paper clip or use a sterile needle and pierce through the nail to the spot and usually will the get a small amount of dark blood. Draining them does usually pretty dramatically improve the pain from them.

Trauma: with added weight especially hiking more pressure is forced to the toes for added push off and also ground force pushing against bottom of toes into shoes causing trauma