I breed mealworms and grainmites are a thing that happens to us from time to time. As others said, they look like grain mites. Seeing it first hand many of times they likely are in my opinion.
Clean up well and throw out and open boxes you have of any grain, oat, flour, bran, cereal because I assure you they're in it. That includes crackers, dog biscuits, dog food, etc., they're extremely easy to deal with though. Lock everything up in tight containers that you plan on keeping, vacuum and wipe down all the surfaces you see them on. Dont leave out food (animal or human) while dealing with it.
You likely brought them home from an infected food item OP. Mine always came from no name oats from walmart so I stopped buying it.