What is this painful knot under my ear on my jaw bone?

It is on the left side, its the only one, feels about nickle sized and moves around under the skin when I press on it, it is also very sore when I touch it, Is it a swollen lymphnode? I am not sick and I havent been sick for a long time, I may be a little congested but its barely noticable, what is this is it a cause for concern?