Unfortunately, and I know this is not what you want to hear, but resting a torn muscle or ligaments are the best medicine. Adding warm moist heat, so for this case being such a large area, bath soaks or a low heating pad will help stimulate blow flow to the torn/over strained area will help as well, and can be followed by ice to help the stimulation. 10 minute increments of each at a time a couple times a day or when you can. It sounds like there are more muscles involved than just a hamstring if it is going in to the groin and down into the calf. Regardless, for a strained muscle(s) the suggestion is/are still the same.

Take the time to heal. Do other exercises that do not involve stretching the leg for now. Take care of yourself and don't over do it so it has a chance to mend. Unfortunately, it will take time. Hang in there and sending wishes for a speedy recovery!