We had an issue similar to this about 2 weeks ago. Our dog got into a fight with another dog, and our dog lost, our dog got a HUGE chunk bit out of her leg. Yes gapping hole, could see the muscle and all, she limped for about a week. We did nothing. The only thing stitches would do would allow it to heal faster and prettier. I know this sounds mean but a mixture of cheyane pepper (spell?), yes the hot chili powder stuff, mixed with hydrogen peroxide to make a paste. Have someone hold the dog down, and someone pack the open wound with that paste you made. Then wrap it, if you can, with gause so she can not lick the paste. That keeps infection out and allows it to heal quicker.
Once she starts licking her wound herself, do nothing else, she will heal it on her own. Good luck.
by the way, we did this and our dog is perfectly fine and her HUGE hole is not a hole at all anymore.