You say full-grown. Do you mean it's a puppy that's pretty big already, like six months old? Or is it an adult dog? Can you describe the situation (where was the child, who else was there, what happened exactly, has this happened before, how did the owners deal with it, etc.)? Can you show us a picture of the bruise?
The short answer is that it's totally unacceptable. I'm really sorry this happened to your child. I would be extremely pissed off too. I do think we need more information to best help you deal with the situation (because even if it was a puppy, it needs to be dealt with). For now ice and arnica will help a lot. That's really awful. :(
We've actually had 2 incidents with this dog. Last year, we were visiting in their backyard with the kids. I was walking across the yard, and wearing a long, flowing skirt. The dog always gets excited and is a jumper, so she was jumping around us, and then bit me on the leg out of nowhere. The owners said she had never done that before, and it must have been because of the skirt. Whatever. It hurt quite a bit, and left a giant bruise, but only took off a little skin, no blood.
For the rest of that year they tied the dog up whenever my kids went over there, and I was just careful to keep an eye on them. Today my son was over there for the first time this year. My mom was over there with him, so I didn't see it happen, but according to my mom, my son wasn't doing anything, and the dog just bit his leg with no warning. My son says he was running with the neighbor's grandkid when she bit him.
I heard my son screaming and met him in my parents' backyard, he had a small bruise (which I know from experience will get much bigger), and the top layer of skin was scraped, pretty much just like the bite I got. I totally flipped. I was pissed off and screaming that I was calling animal control (I might have dropped an F-bomb or 12). I didn't talk to the neighbors, but my mom tried to smooth things over with them later (that's just how she is).
So I think these people are totally irresponsible to be keeping this dog around their grandkids, but my mom is trying to convince me that while it's not a good thing, it's really not a big deal. She equated this with a cat scratching a kid. I don't think so. Even if this dog is just poorly trained, and not vicious, it's still a threat to kids.
I'm not letting my kids over there again, whether the dog is out or not. The neighbors have an invisible fence, so presumably the dogs won't come in my parent's yard. I'm not going to call animal control, but only because I don't want my parents to have to deal with neighbors who hate them.
I guess I don't need advice, so much as validation. I don't think I'm overreacting here, am I?
Yeah, that sounds like a real bite. Scrapes and a bruise -- not good! What kind of dog is it? I'm wondering if it's a herding breed? It is a big deal when a dog is biting, even when it's not totally vicious. I wouldn't let my kids around the dog either. It sounds like it needs to be trained and that it possibly has herding instincts that need to be appropriately directed. A dog should never put their mouth on a person. At all. That's unacceptable.
it sounds undertrained and over excited, it was probably never taught to inhibit its bite. It sounds like the dog was playing and overexcited which means that it wasnt aggressive. I would be angry, but at the same time it is your responsability for keeping your child safe, the people should not have had it offleash around kids but you also should have checked first.