I think it comes down to the fact that if he isn't able to partake in the normal daycare day that he needs to stay home. There is the risk factor of further injury in a group environment and as a single caregiver environment, isolation or separation from the others isn't realistic in my opinion. I think at least a few days home to heal is called for. Also a two year old on pain meds indicates to me a pretty clear picture that this child is in a fair bit of pain. Again not someone who should be at daycare in my opinion.
Did mum give you a heads up about this prior to drop off?