Noob to stock trading and taxes question

[sMethod]

This past year the goverment saw me making zero dollars in income and pratically zero dollars were spent on paper so I wasnt going to file this year but then I remember I cashed out 100 shares of disney, the first real trade iv made my entire life.
Should I still file?
Do I have to file if I basiclly look like a dependant to the IRS?
Has the stock already been taxed or do I still have to pay?

Thanks for helping out a rookie.