I'm 20 years old and I have Gynecomastia. Is surgery is the only choice for me to correct it?

If you truly have gynecomastia, surgery is the only effective treatment.  See a board certified plastic surgeon in your area for an evaluation.  Good luck
and be safe.John T.
Nguyen, MD, FACS, FICSDouble Board
Certified Plastic Surgeon

Most men at your age who have gynecomastia have had it since their teens.  The excess glandular tissue that has developed while you were a teenager will not disappear with time.  However if you have fullness in your breast area due to general weight gain then weight loss may be beneficial.