Hi Matthew 158315,
It seems like you have re-injured your hamstrings.
Muscle lesions generally take 20-30 days to heal (depending on several factors). However, from a biochemical point of view the healing process continues for months. It is paramount during the recovery process to properly stimulate muscle fibres. Neither low nor excessive loads are indicated. I know that it is difficult to know the right amount of load, but it key as it properly helps muscle fibres healing.
Previous muscle lesions are among the most important factors for reoccurrence of injuries. Other factors such as biomechanics, posture, muscle flexibility, muscle imbalances and many others need to be considered in cases like yours.
If you have not done so yet, I would suggest to integrate your progressive muscle strengthening program with Nordic hamstring eccentric exercises. Better if supervised by a sports therapist. Nordic hamstring eccentric exercises are demonstrated to be among the best exercises for injuries prevention.
Let us know how your injury evolves.
Regards