Hamstring injuries can be frustrating and easily recur if you don't do the appropriate rehab. I'd recommend eccentric strengthening exercises. Working a muscle eccentrically is the fastest and most efficient way to strengthen a muscle.

Long term you may want to look in to plyometric exercises as a preventative approach as well as adding power to your running.

A common fault among runners is to overuse their hamstring and "underuse" their butt muscles so some butt strengthening is also a good move!!

A physio should be able to direct you to the appropriate exercises.

Rachael
Physiofixme: Physiotherapy Online