Pain inner knee and sometimes i feel a knot behind that knee, no swelling ?

Knot, no swelling?: that might be a fine distinction indeed! there is a bag of cushioning fluid inside the knee called a bursa. Practically any inflammation casues more fluid to accumulate inside of it. When it is seen behind theknee whree it has popped out, it is called a baker's cyst.

Knee pain: We can enumerate few differential with this symptoms, could be bursitis, meniscal or ligament injury or arthritis changes ( rare at your age), if pain does not improve within couple of weeks, consider physical exam and some xtay.