To dream that your child is in pain and suffering a lot, shows that some of your saying or actions are hurting other people. This dream suggests to be more tolerant and listen what your children has to say. It is also very normal to worry about things that are unnecessary to be worried about. If you feel the pain during the dream, you might have psychological problems or you are in actual pain that is felt through dreams either.
Read more about dreaming of Pain in other dream meanings interpretations.