Hi Sanantha, look seeing your doctor is a good thing, but to be it sounds very much like ligament trouble, for a start I would ice pack it 3 times a day for 20 minutes, the idea of this is to bring blood to the knee ligament and help heal it, and tens tretment through a physio, swimming breststroke leg movment only is a big help, and you need to end up doing 1K a day.
Ιts OK I ddi all this a couple of years ago and it worked for me and I'm now 65.
Have you put an ice pack on it? I have had knee surgery on my right knee 5 times - each time the orthopedic doc has recommended icing the knee for a few minutes every day. I had the "bad stuff" scraped out from the underside of that knee 4 of the 5 times for surgery. The first time was for a torn meniscus after bumping it on a file cabinet at work. Seeing the doctor is ALWAYS a good choice when a new pain arises - especially one that doesn't seem to want to go away. Good Luck to you!
Also, I'd like to add.... I am 24 years old, female and weigh 128lb