I am in agony here..?

You are using muscles that you are not used to, torn ligaments can take a very long time to heal soft tissue injuries can take 3 months, you must try and move about as much as you can with your crutches otherwise you will be back to square one when you use them again, think of it like exercising for the first time it takes a few goes before your muscles settle down, if you are no better after a couple of days see your Dr. You could take something like ibuprofen to ease the muscle pain.