Suggest Treatment For Knee Pain And Stiffness

Hi, I am almost 16 years old. I'm about 5'1, and 130 lbs. My knees tend to hurt a lot, and always feel like they NEED to be popped. Sometimes they pop involuntarily. But usually they become so stiff that I feel like I HAVE to pop them or else the pain wont go away. Soon afterwards, they will be sore and hurt. My dad says that its just because I'm growing, but I don't believe him... What should I do?