Knee pain, what to do?

Hey guys I’m about to start on the pct and I’ve been training walking and working out every day and my knee hurts. I’ve had pain before, the first ever long distance hike three years ago I had knee pain for the first time it was terrible. I’m not sure what to do and I’m worried that my knees are going to stop my hike. What do you do about knee pain? Stretches? Massage? Is my knee pain being caused by something I’m doing wrong or tight muscles ? Thank you for any advice. I don’t want to ruin my knees for life.

Pain is often originating on the top of my knee or the bottom.