I learnt the hard way nearly a year ago, should have left the bike in gear on an uneven surface and it rolled forward off the stand... I wasn't close enough to catch it on my thigh and hold it, instead it caught my knee side-on and folded it sideways, rupturing my anterior cruciate ligament :'( the pain was unbelievable and ended up with an operation to rebuild it in November. If the bike's going over best just let it go or you risk really hurting yourself trying to catch it... Might be an idea to use the side stand next time, though you've no doubt figured that out for yourself. Get the knee elevated and put an ice pack on it to reduce the swelling. If it still really hurts tomorrow, go to the doctor. If you go to A&E be prepared to wait around for ages and be told "it's soft tissue damage" >
