Probably no long term damage, would be a guess.

As to stretching - a massage therapist taught me how to do PNF stretching of the hamstring. _really_ helped me as a runner.

While you probably should not stretch much till healed - once healed:

While standing, rest a leg on something solid, roughly picnic table height ( what I used to use in the park) and start a good stretch of the hamstring by bending forward from the waist - when you have a good solid stretch - maybe 80/85% of your total bend - push down on your leg at the ankle, while attempting to push your leg _up_ against your hands - you can feel the hamstring and related muscles relax more, then smoothly bend in for the rest of the stretch.

The basic principle here is - when you activate (tighten) a muscle, the opposite muscle relaxes - so when you attempt to push _up_ with your leg, the hamstring relaxes more and this allows you to increase the stretch.

Absolutely killer hamstring stretch.

There is a good bit available now on PNF stretching, if you wish to research it further