Slowly straighten the knee until a stretch is felt in the back of the thigh, trying to get the bottom of the foot to face the ceiling, one leg at a time.

Listen to your pain and do activities accordingly. That means you can start exercises but should stop exercise as soon as your pain starts. You should apply hot pack or do hot water fomentation over hamstring and stretching before starting your workout and apply cold pack after you finish your workout. If this is not helping you should consult a Physiotherapist for proper treatment. Hope this will help

No. Firstly  tk physiotherapy treatment  for proper cure than start gradually otherwise problem will increase

Consult the Physiotherapist near by and start with light strengthening exercises specific to your injury. After some days of that u can resume to ur gym also

Consult a physiotherapist for an evaluation, it seems like your hamstrings are not completely healed. The healing period for muscles is 6-8 weeks. Stretch the hamstring few times a day followed by active knee flexion movements to maintain the normal muscle length.