I was diagnosed w/ TMJ 16 years ago. That first acute period was my worst ever! Since then I've only had "flare-ups" that I've learned to manage. So in my answer to your question, "will the pain get better?" I would answer yes.
Here are some things that cause my flare-ups: 1. Chewing gum (I don't anymore) 2. Talking too much (esp. with the phone propped between my jaw and shoulder.) My husband says TMJ stands for Too Much Jabbering- In a way I guess he's right! 3. A cold--you may not realize it but you clench your jaw muscles when you sneeze, cough or blow your nose! 4. Propping my chin in my hand, like when sitting at a desk for a long time. This puts pressure on the TM joint. 5. Childbirth--clenching during labor!
6. Any kind of extended stress.
Here's what I do to manage the pain during the flare-ups:
Ibuprofen, as has already been mentioned. A heat pack- I made my own by sewing uncooked rice into a canvas bag. I heat it in the microwave before use. It conforms nicely to the angles of my jaw. Massage-- over the years I've learned just where to massage my TM joint w/ the tips of my fingers to help relax the muscles. I do this after the heat w/ my mouth open and relaxed (this sort of opens up the joint.) I've heard of exercises to stretch the muscles surrounding the joint, reducing the spasms. But I could never find any specific info on these exercises, so I made up my own. I just open my mouth slowly stretching as wide as it will go, 10X. Then I extend my lower teeth in front of my upper teeth as far as is comfortable, 10X. During a flare-up I do this a couple times a day and follow w/ massage. If anyone knows of "real" TMJ exercises please post them!
Like I said, I've never again had the same debilitating pain of the initial phase. I hope that you can get into "remission" quickly too. I've been on some websites and found that there are many treatments but none are 100% guarenteed to work. Since I can live w/ my TMJ as it is, I chose not to risk worsening it by trying any treatments.
I know what you are going through and wish you the best.