Small green dot/light

There’s like a small green dot it’s light in the middle of the screen. I restarted my phone and it’s still there. When the screen goes black when I turn it off it goes away but as soon as my screen comes back on it’s right there says the small green dot of light. I didn’t have it all day until a few hours ago it just appeared I haven’t dropped it I haven’t wet it or anything. How do I remove this? Much more green and bright than pictured.