Be careful not to be too dismissive with "just a pulled hamstring." Here's an interesting article about various hamstring injuries
. They're not all the same. One injury that happened to me was a complete avulsion of the ischial tuberosity...the hamstring completely tore away from the hip bone. Three years later, I still suffer from an uneven stride, instability, and a much slower pace. But thankfully no chronic pain.
This injury can happen to young runners up to age 25
...and to older adults whose bones have begun to weaken. The problem is that the avulsion is not immediately recognized by many doctors. As a result, if the standard advice of "ice and rest" is followed without further diagnostic effort, the delay may make the injury very hard to repair. So take care of your hamstring!