My mum always told me that your eyes will go blind if you cry too much when I am crying. I know that crying for a long time can bring us some problems, such as red and pain and often we will get swollen eyes too. I think you can relieve your eye pain by apply some artificial tears into your eyes. Maybe the remains in the tears such as salt in our eyes lead to eye pain.
I think your sore eye is caused by rubbing your eyes when you are crying. And your use great energy to cry will make the muscles around your eyes pain. It is a very common problem to those who are crying. And it doesn't need any special kind of treatment for they will recover after some sleep or few hours later after stopping crying.