Knee injury help

[MHSathlete]

Hi about a week ago I was lifting weights for spring football, squating relatively heavy weight 355lbs immediately after the work out I felt no stiffness or pain the next morning I woke up and felt painful stiffness in the posterior of my knee. I couldnt seem to strech it out. Today my knee cap dosent feel right and the right outer and inner side of my knee cap are very tender and in a lot of pain along with intense stiffness. Now I can barely walk or put any resistance on my knee. When I went to strech I neiled on my knee for a second and it felt as if something shifted or was moving poping out place. Any ideas for care any diagnosis? any help thanks