Hello and welcome to the board!!!!!!!!!!!!!!!!!!!!
I would definetly go see your general dentist first before anything else. He can see if there is an infected tooth. But you also could have tmj. If you are grinding when you sleep you are causing a lot of wear and tear on your teeth and also your tm joints. Lock jaw is a common cause of tmj (a lot of us have it). When you go see your regualr dentist tell him that you grind your teeth. With or without pain you still grind. Do you have any other symptoms? There are also some people who have tmj with no pain at all. Your dentist can also refer you to a tmj specialist. It depends on what you decide to do but both specialist and dentists can make a splint for you to wear to help stop your grinding. I would be weary about who you go to for your splint. I have been having troubles on this end. If I were you I would have it made by a specialist. This is the more expensve route but you are able to get a better diagnoses then from a regualar dentist who claims they do tmj.
Since you say that your jaw is locked or pretty much locked try to loosen your muscles around your joints. Apply ice and don't chew on anything. I suffer alot from a locked jaw and my diet has changed to basically liquids and some soft foods. My physcial therapist also says that it is best not to move your tongue too much.
One more thing, an specialist has teh ability to see if your tmj is joint or muscualar. This is a very good thing to know so you have more of an idea of what you are dealing with.