Betta Fish: What’s this?

Please don’t grill me this is my first ever time keeping a fish or a tank at all but due to some awkward circumstances and timing I got my fish even before I got my testing kit and more substrate for my tank, I managed to get plants and I had attempted a cycle without the kit by letting the tank sit with beneficial bacteria for around a week, the kit and the substrate are on the way but in the meantime I noticed these little spots on the bottom of my tank, what could they be? My fish pirate is doing really well he’s swimming and eating well and loves playing with me and his fins aren’t clamped