blue and red dots in a dark room

Here's a picture taken at a balloon festival early in the morning with a Nikon Z8:

Here's the background blown up and brightened a bit:

That's digital noise. Or this

This is from the Lost Kids booth. All that variation is just noise.

This is what it looks like when you digitally remove the noise.

Done with Lightroom Classic.

What were you trying to take a picture of--I don't see a subject. Apparently the camera didn't either, so it ramped up the amplification until you can see the digital noise.

"Noise" is always there, very dim, but usually you don't see it much unless the subject of the picture is not much brighter than the noise. In film this was called "grain." In digital sensors and analyzers it comes from random firings from heat and such. For astronomical pictures of very deep dark space, the sensors must be cooled to near absolute zero to reduce the noise. I'm thinking the phone, though, wouldn't work well immersed in liquid helium.

The noise probably isn't dust. That would show if you used a flash, but with no light you won't see dust any better than anything else. It is more likely random digital noise. It's not a defect, and you will see less of it when there is enough light to see something.