Hi bhudiya
Your first step should be to see your GP to get confirmation that you have gynecomastia. If your GP isn't on the ball and doesn't know what gynecomastia is or how it can be treated ask to be referred to a specialist. At your age if the gyne is hormonal (quite likely given when you think it started) then you should get referred to an endocrinologist. If you don't, then possibly your GP isn't that clued up and again you should ask for a second opinion.
Don't live with it hoping it'll just go away. Don't delude yourself that working out will somehow get rid of it and spend years heaving weights at the gym. Breast tissue doesn't respond to exercise, otherwise Jordan could have save a lot of money!
Take a first step, see your GP. Good luck!