iPhone 11 not responsive

I've had my iPhone 11 for almost a year now and haven't had any issues, but today I was using FaceTime and when they hung up, there was a grey/black square in the corner of my screen where their image would be if the call was still connected, except that it was a square instead of a rectangle. After that, they tried to call me back and all I got was the grey/black screen again. I can swipe up to go back to the Home Screen, as well as close any apps that were open, but I am not able to interact with any of my apps, end the call, or even turn off my phone. Siri works to call/text, but not to open any apps. I can swipe down to see past notifications and the shortcuts to the flashlight, stopwatch, calculator, etc. I can also screen record, but I can't take a screenshot. If someone texts me, I can swipe down to respond, but am not able to open Messages from there. Also, the screen still automatically goes to sleep and I am able to open it back up and unlock it. I guess what I'm asking is what's wrong with it and how do I fix it?