Like See and Mk mentioned, probably either maggots of some kind, or Enchytraeus buchholzi (usually called pot worms by vermicomposters in the US). Both are helping with the composting, and do no real harm, though of course maggots will hatch into flies of different kinds, which of course can be a nuisance in an indoor system.
Pot worms are mentioned on page 5 of this document: https://dpw.lacounty.gov/epd/sg/tech_sheets/wc_info.pdf
. Apparently they thrive under more acidic conditions. So you may want to check out the pH of your bin. Pot worms themselves are not a problem, but they *could* indicate that your bin is becoming overly acidic, which wouldn't be good for your composting worms in the long run. Many people add ground eggshells or oyster shells to make their bins more alkaline. A Google search of "pot worms in vermicompost bin" will give you a whole lot of info on these little critters and what they may indicate.
If you have maggots, you will probably notice fruit flies or flies around your bin soon. Burying the waste under the bedding and/ or adding a screen can help with this. Another helpful thing can be blending your food waste, or freezing it before giving it to the worms. If it is broken up more, it allows to the worms to start working on it faster, which means less time lying around creating habitat for maggots. Large pieces of fruit, especially, take forever to be accessible to worms, and provide perfect maggot habitat in the meantime.
One thing that I overlooked when I first started my bins, was the importance of balancing the food scraps with plenty of bedding material. I used lots of bedding material when I first started up the bins, but in order to keep the carbon-to-nitrogen ratio high, it's important to keep adding bedding with almost every feeding. Or once in a while add a very large dose of bedding. Thankfully I watched a video on this before it became a problem. But it might be the most important thing you can do to keep your bin balanced and safe for the worms. I use chopped cardboard, and also partially composted leaves/ forest litter from the woodsy area at the back of my property. The worms seem to really love the forest litter, and I think it will make really high-quality castings. When I collect bags of fall leaves (leaf season is right around the corner here in Texas), I am going to add a nice layer of them to the areas in my woods where I removed litter, to hopefully not upset that little ecosystem as much.