A.R.
While I can't speak as a mom who has had a child bitten, I can speak as a child who was bitten. It was the day after my 14th birthday and, as you might imagine, I thought it was the end of the world and my poor father who watched it happened was desperate to make it better. I had a simple surgery to fix the tear from the corner of my mouth and am fine - the scar is barely noticeable now nearly 14 years later. I can also say that I have a dog and a 2 year old child...
Your little guy will be fine. He wont remember and you should not feel bad for an accident - there was likely nothing that you could have changed. He will not be any different as a person for what he has gone through.