Small sand pile on floor. Are they from bugs?

Ants can do it.

Is there a small crack in the ceiling above it?

If it is a small , tight pile I’d say ants or termite. If it is spread out I’d look up and see if there are termites in the ceiling.

Either way, some Raid or Terro Ant products are in your future. I’d like Terro liquid ant traps best. Just put them near the ants and walk away. Don’t spray don’t do anything just walk away and don’t look. they take it back to the nest and in 2 days your problem is gone.

If it was outside, I would think it was carpenter bees. They drill into decks and siding making perfectly round holes and leave a pile of sand.

Probably ants.