Well, discomfort around the knee joint could be caused due to a number of reasons like injuries to the bones/ ligaments/ tendons, injuries to internal knee structures, infections, inflammations, dislocations, degenerations, growths/ masses, vascularity or mineralization issues etc. Without a clinical evaluation it would be difficult to determine the cause in your case. I would suggest an evaluation by a primary care physician or a sports specialist (whoever is more convenient to see). Depending on the cause diagnosed this can be managed accordingly or specialist care may be sought. Meanwhile I would suggest resting the knee. You could use a crape bandage or a brace for the same.
Hope this is helpful.