Left knee joint pain , pain until my tibia get pain .. what can i do?

that day i was walking & i didnt know there was a small stair & i hurt my left knee by pressured on 1 leg .. very pain ! after that , i felt like i still can walk so i juz leave it then the nx day it was swollen so i juz use the medicine rub my knee but is not work at all is getting more pain so last 2 days i went to c doctor & she x-ray my knee & she say ok nothing happen to my knee she say is tissue problems .After when i went back home & c the x-ray clearly & go to search google how is the normal knee look like then i felt that my patella is in a superior position so that i realize that is the knee joint problem so i slowly try to push down my knee & it really move but i try to do the same thing to my right knee but my right knee not moving at all .. so i can say that is the knee joint problem .. im so sad .. i dont know what to do .. plz hlp me ~ Thank !