Mystery knee injury

I already have poor and weak knees due to hyper mobility, however at the weekend I jumped off a 3ft wall thinking I’d make it fine, but my knees gave way and one of them bent back behind me a little. I didn’t feel much in the moment, maybe due to drink, however the next day I was in so much pain and I’ve been limping since. I can put weight on it just fine, however the inner of my knee aches and I can’t bend it very well, squat down to sit and if I am standing after sitting down, I get an intense cramping in my knee and thigh. Does anyone know what this sounds like and how I can help it? I have a bit of a fear of the doctors and also a massive project at work I have to be present for. Thank you!!