Sons weird reaction to cow milk

Hey everyone, my son is 16 months old and he has was strictly breastfeeding until around 15 months. He drinks one bottle of NIDO at night but for the most part he drinks water. I went out of town all day on Thursday and my husbands friend watched my son and he gave him a bottle of dairy milk. An hour or two later we picked my son up and he started vomiting in the car and ever since Thursday he’s had a pasty color of diarrhea. I made an appointment but he can’t be seen until January 10th. He has no other symptoms but has anyone had a similar experience?