The basic difference for social justice and individual justice only rely on the magnitude. Social justice seeks fairness for the whole social group while the individual justice only seek fairness on personal level. BUT, in order to achieve true social justice, that society have to achieve personal justice as the foundation for the social justice
go to your teacher for help and explain that you haven't went over it and ask for help to better understand it and if that doesn't work do more research on the topic to understand it yourself