A.V.
You need more info. I would find out under what circumstances does he do this? Is it a certain time of day? Is it a particular child? Is it when there are a certain number of children or when the daycare provider is distracted? Usually children bite to make a point when they can't speak yet. My own DD bit a child at daycare and was bitten (in the same room with me at a family event - she and another 2 yr old were playing in a corner and all of a sudden my DD screamed....). If it persists, you may want to find a different type of setting for him.
If it's a home daycare, see if he does better in a center. If it's a center, would he do better in a home daycare? We actually had more issue with my DD biting ME and only ME - she'd come up and bite me on the leg when I was at the computer. She wanted my attention, so I had to teach her that she doesn't get Mommy's attention that way. Does he want the child's attention? Does he want the toy? What does the provider do to diffuse these situations?
If you do not already do so, consider teaching him to sign. If he can tell the teacher "hungry/tired/milk" he may feel more in control and less likely to bite.
One of my friends had to move her toddler to a different center (in her case, a home daycare) and the child stopped biting. Sometimes kids need a different environment to get past this issue. I mention this because if it comes down to it, you're not alone and you're not a horrible parent.