M.J.
I'm normally one to say "it's a common phase, don't worry about it," but what concerns me here is that the childcare provider didn't tell you about the injuries and isn't taking action with her grandson. Red flags to me. Our daughter's home-based daycare had a biter and she often came home with marks, but the provider always told us what happened. She didn't always witness the situation, but most of the times she did. And I felt like she was doing the best she could to deal with the situation, more than just saying "stop." Personally, I would look for another daycare provider. You may not be able to avoid biters (they're everywhere in daycares), but you can at least feel like the provider is doing the best she can to deal with the situation. And bruising, with no explanation? Yikes ...