What is this? What to fix it?

Can anyone explain what this hole thing is between my teeth, up until a couple weeks ago that area was covered in gum tissue but it seems to have died and now the gum is lower than it used to be. Doesn’t hurt at the moment but if it does need fixing I’d like to know what kind of fix it will need so I can find out how much it’s going to cost. Going to have to go private as the NHS wait times where I am are year plus long.