Can social media be used as a tool by one individual to successful push change in society?

Of course it can. Social media is a great tool to enhance democracy and positive changes in society. It can be used for notifying people for new humanitarian events (collecting money for various causes, gathering supplies for the homeless people). It can also be used for motivating and calling people to organize and attend the protests against government or other social anomalies in society. If someone firmly believes in their causes and has courage to pursuit them, social media is a powerful tool if used correctly.