Internal Knee Pain. Advice accordingly.

I have been experiencing some pain in my left knee. It must have started about two weeks ago. The pain is internal, in the core of the knee joint. It aches occasionally but when the body is warmed up during a workout, the pain seems to decrease. However, lately there has been a rise in the pain as I have started running at a faster pace for longer distances (about 5 km). Even with the warm-up, there is some feeling of a strain being exerted on the knee. Another point to be mentioned would be that during the action of standing up from a seated position, there is some aching sensation in the knee. I have researched a bit and I think it is a Grade 1 MCL sprain. There is no swelling at or around the joint itself. Kindly suggest the treatment and duration of healing process. Also, I do not want to miss out on the running as I want to make the most of my ongoing vacations. So, please give some advice accordingly.