Is there something wrong with my monitor?

It’s gonna be hard to explain, but I left my pc on the dark souls 3 menu screen, where it shows "dark souls lll" in big white text across the screen. I left it there for like 30min. when I came back, I started the game and it still showed the dark souls 3 text across the screen, it was quite faint. I got scared so I turned off the game and it was still there. I turned off my pc, and it was still there it disappeared after a while. Should I be worried? Is my monitor dieing or is there something I can do or maybe is it normal? And lastly is there a name for this because I have no idea what to google to make sense. My monitor is LG 27GN800