I am a 19 year old male. I was snowboarding and I fell at an awkward angle. My right knee bent inwards (toward my left knee) and I felt something pop. I sat down and took the boot off the snowboard but could barely move my leg. My knee started to feel like it was burning (almost like a heat pad was turned up too high and wrapped around my knee), but after a few minutes the feeling went away and I gained back some mobility. I stood and was able to put weight on it and bend it, so I rode down to the bottom slowly. It has been two days now and I can pretty much walk normally now except when I first wake up or when I accidentally twist it a little. I initially thought it was just a sprain because I could move around on it again so quickly, but a friend told me when they tore their ACL they could still move around on it. Does this sound like it could be a serious injury?