Endodontists specialize in the nerve of the teeth and from what you're describing it sounds as though your nerve is irritated, dying or is already dead. Sometimes after having dental work done (such as getting a crown
placed) the nerve can be irritated and just needs time to relax and go back to normal. Sometimes though, the nerve can be permantently damaged to no fault of the dentist (it can just happen sometimes) and will need a root canal
If your gums are inflammed, then there's probably truth to what your dentist said about getting the gums cut back as the inflammation
will usually not resolve itself and will only lead to more destruction in the mouth unless it's corrected by the minor surgery
. Gum sensitivity typically won't lead to the nerve pain
you're describing however, so this tooth might have more than one issue going on with it.
Best of luck.