Is the feeling on the outside of your knee? Almost like your bone is grinding against something? Can you also feel pain up by your hip? Almost like it's swollen? If so, it's probably your IT band.

I've struggled with this since my half marathon training in 2016. Like other posters suggested, you should probably make an appointment with a PT. And if it is your IT band, invest in a foam roller and make sure you're rolling your leg daily. Also be sure you're stretching and opening up your hip flexors, as well as icing after activity. Try working on building up strength in your glutes with resistance bands, and do some hip thrusts, lunges, etc.

Your best option is to probably relax for a week or two, though. Especially since yours sounds pretty severe. You don't want to exacerbate the issue and be sidelined for months. Go to a PT and get a professional opinion, though. They will let you know when and what kind of activity you should be doing, and can even help you with strength training.

I was perusing this sub for IT band posts this morning, and came across a post where a user suggested a Pro-Tec IT band wrap from Amazon. I looked it up, and the reviews are killer. I ordered it straight away. In no way does it solve the issue, but it stabilizes the ligament so that you can run mostly pain-free. After seeing your PT, this might be something you want to look into! It's cheap as well ($17).