This product was mentioned in
with an average of
I had some similar issues when I started out and ended up buying some compression sleeves for my knees (and taking a couple of days off). So far they've helped a lot and my knees have gotten a lot stronger since then so I probably don't need them anymore.
That said, if it's not gone after a couple of days of rest, definitely check with a doctor.
I like to wear compression knee sleeves during the entire hike. It helps stabilize the knee joint and lets me go a little longer without feeling pain. I also recommend using poles, since they can take some of the weight off your knees.