Thanks for posting your query here.
Please don't panic.
It is quite possible that the milk in old bottle may have been bit stale, due to time elapsed since it was made.
I would suggest to keep an eye on what symptoms appear over next 48 hours. You may also notice some changes in his stool colour/consistency or smell.
If there is any vomiting
, please try anti-sickness medicines available over the counter.
Please revert back to us if you any of these symptoms appear, should you need any further help.
All the best
Dr Tejas Shah