It might be a harmless fungus or mold that sometimes forms on moist soil surfaces. It's generally not harmful to your plants, but if it bothers you, you can gently scrape it off. If it's insect eggs, that's a bit trickier. Identifying them without a picture can be challenging, but if you suspect they're insect eggs and you want to salvage the soil, you could try scooping out the top layer where you see the eggs and dispose of them. Then, you can replace it with fresh soil. You can check out the post on how to get rid of flying ants in the house. They might shed some light on this topic, too.In any case, keeping the soil well-drained and not overwatering can help prevent these issues.
