Try role play with him on the scene and guide him how to react. Normally, I will not say "it's ok" when such incident happened. Instead I will ask how he is feeling and acknowledged it, then share how I will feel in the same shoes then explain what is the best way to handle in future. Also I allow my children to have a comfort zone, we don't force him to play with other until he feel safe and comfortable.
Kids are like little adults, sometimes we need time to warm up too.
Read more