I am so sorry to hear that he has developed diabetes at such a young age. It’s unfortunate but the truth is it can effect children of his age and we just have to deal with it . The sugars will surely get controlled but need bit of patience from your part. The insulin needs optimising in order to get that. I am not sure what regime your are following. You might just need to have regular monitoring of his sugar levels and discuss with the diabetes specialist to see what changes need to be made to the insulin injections.