Hi Jay,

Thanks for posting this picture.
Yes, that is a large cavity but it depends how deep it is as to if it can be filled without the nerve being involved.
It looks like the extraction site has not healed closed yet. Usually it is best to wait until the hole has closed before drilling into a tooth next to the extraction site. The air from the drill can cause debris to blow up into the socket which could cause an infection, etc.
Make sure your dentist looks at this site before he attempts to work on this other tooth.

Bryanna