What could be causing my knee pain?

I tripped over something in my room a couple of days ago, later that evening i had pain in my knee and could hardly walk i had to hop. A few days later the pain is still their and i can hardly walk, but also i moved my knee and heard something crack and then my when numb and tingly. im 16, if i tell my mum she says im fine and tell me that i will be ok, what could be wrong. will i need crutches