What to do about Knee pain?

I'm 16, and I'm very physically active. I'm in dance, rodeo, trick riding, and softball, and I did three years of competitive cheer. My right knee often hurts when I get done with practice. When I move it, it doesn't feel smooth, and occasionally clicks. What can I do about this? Please help!! Can I stretch it or something? I don't want an injury or anything!!!