Once a tooth is extracted, the blood that forms in the socket coagulates "plugging" the socket. This provides protection for the socket.
If for some reason the coagulated blood is removed, you can get a "dry socket", which, can be quite painful.
The bone that creates the socket will, after time, resorb (shrink). That's why new dentures often need to be relined after some time. The bone resorbs & now you have a space between the denture & the gums. I would think that if you have an open socket after an extended period of time, you probably need to get in contact with your dentist.
I've seen instances where the dentist will suture the gum tissue together, closing off the socket & eliminating future problems.
Good Luck.
Joe F. (Buffalo)