How do I avoid Lens Flare when taking photos on iPhone 13?

That is Lens Flare and is quite normal, especially when you are taking photos of BRIGHT lights as your examples are. You can help to minimize or even eliminate the flare, which was plainly obvious on your iPhone screen before you took the photo, by angling the camera different to the lights. But taking photos of bright lights will do this and is not indicative of any issue with your cameras in your iPhone.

There is no way you couldn't have this, it is caused by reflections off the camera lens. You just didn't notice it before.

What is lens flare?

https://photographylife.com/what-is-ghosting-and-flare#:~:text=Lens%20flare%20occurs%20when%20a,being%20present%20in%20the%20image.

SkillsOP wrote:

so i shouldn’t worry? i don’t think i had this when i first got my phone , not to this extent at least i even have photos where the camera was pointing at the sun and light and it was never like this.

NO, you shouldn't worry. Every single iPhone you could take the same photo with or for that matter just about any camera, including my Nikon DSLR, with a lens costing appreciably more than my iPhone 16 Pro Max would capture lens flare of such bright lights. You're seeing a reflection of the lights off the sensor, which as I suggest, can be minimized or eliminated if you are more careful with angle of the camera from what you are taking a photo of.

So it's possible you changed the settings for your camera. The newer phones pick up lens flare more because the newer sensors they use are more light sensitive. Also the software they use to enhance night photography also will pronounce the lens flare more.

"it’s like it’s a small green replica of what emits the light"

That is exactly what it is, an inverted replica of the light source caused by a reflection off the lens.

The reason it shows up green is because of the coating on the lens. Lens manufactures use either a green or maroon coating on the lens to reduce lens flare but it can't completely stop it. Apple uses a green coating on their lenses, hence the green hue of the flare you are seeing.

It's not reflecting off the sensor, it's light reflecting off the lens.

You're right of course.