Thank you for your query.
The most common reason for soreness and pain in the finger tips has been excluded by your mention that you stay in Australia where it is warm these days. Hence it cannot be chill blains. I suggest that you get your son examined by a doctor to know what is the exact problem. Without seeing the redness
it is difficult to make a suggestion. In all probability the redness should settle down.
I hope I have answered your query to your satisfaction.