Unloaded Chunk

I was playing my survival map when I saw this unloaded chunk thing. I tried to reload the chunks by using F3 + A but it didn't work. I also tried to close Minecraft and re-opening it again. It didn't work. I can't pass through it although I could if I go into creative and flew above it but really high up. I also tried to blow it up with TNT. But still no luck. It causes so much lag, so much that it causes the other chunks to not/ slowly load. Please solve this issue. Thank you for your time.