Oh man...been there done that with the horse biting thing.
I was still getting to know my horse when I did something not to smart and got myself bit...HARD!
I had saddled him up and noticed the martingale loop was too far over to one side (where it attaches to the girth). So standing facing him, I bent down and pulled the strap over and in the process, pinched him. Being thin skinned and sensitive, he pinched me back with his teeth! It was the dead of winter & I was wearing 4 layers. A thermal top, under a flannel shirt, topped off with a down vest under a down coat. I still ended up with a painful black bruise on my shoulder blade, that took months to heal. Had it been summer time and I'd only been wearing a strappy tank top, I'm convinced he would have taken a chunk out.
Never underestimate the power of an equine bite! Yeowch!