jaw locked closed?

I don't know how to explain this, our cat was eating some raw meat and suddenly he meowed in a weird way. It seemed like he couldn't open his mouth, i quickly searched online but only found cases when the jaw was locked open. He ate a little wet food before and we gave him some raw chicken bits and then he meowed as if something hurt him. Was the chicken too cold? We didn't try opening his mouth to not do something worse. We tried to give him food but he just licked some of the wet food and drank a good amount of milk. It seemed thst he oppened his mouth when he drank.
The thing is that he is an adopted street cat, as in he appeared on our street and we fed him and took care of him, in the winter he sleeps inside but we can't keep him inside in the summer, he just meows and scratvhes the doors and sprays on everything if we don't let him out. He comes back several times a day to eat and sleep but we can't keep him inside at night. We tried, he meowed until 2am when we let him out.
After this incident he also wanted to go outside, we tried to keep him but he wanted to go. When i picked him up he meowed again and it seemed like his neck hurt.Does he have muscle pain? I'll take him to the vet tomorrow but i don't know what happened...

You need to keep him inside until you can get him to the vet.

Also, is he neutered? His behavior makes it sound as if he is not.

You NEED to keep him inside, even if he howls, until you get him to the vet.  Place him in the bathroom or spare bedroom.

Were there bones in the raw chicken? Let us know how you make out at the vet!

Sorry for the late update and thanks for the quick respone
He's ok now, the vet said he could have hurt his tooth or bit himself or just hurt himself somehow and was probably scared to open his moth. He was fine by the time we took him in the morning, he's eating well, we kept him inside a lot to force him to rest.
There weren't any bones in the chicken, there were small bits of breast and the soft white parts that we cut off.
We're going to get him neutered, i'm just worried a bit that he'll get sad or lethargic, he's old too, the vet said he's around 10-11. Is it safe to perform surgery at this age? I know the vet said he'll be fine but you know, i'm just worried...

If he's in general good health, he should be fine going through the neutering surgery even though he's 10.

You might be pleasantly surprised if there's any change in behavior once neutered.  As long as he's in good health, he should come through the surgery fine.  They should do some pre-surgery bloodwork to check his health, too.