I know you're gung ho to get back into the program, but you have to listen to your body. If you try to exercise before your hamstring has healed, you risk making that injury worse than it already is. Good health isn't just about going to the gym every single day. In fact, a person doesn't have to exercise every day to be healthy. What to do ? Take it easy. Don't assume the leg is better just because it feels okay. You may start running and the next thing you know, you're limping back home. Can't tell you how many times that's happened to me.
Take a few days off. Just because you can't run doesn't mean you can't exercise. Do upper body or core exercises while your lower body heals. don't do anything to aggravate that injury, give it time to heal. In few days you can slowly ease back into a routine.
Because you have to ask yourself this question,"Do you want to take a few days off now to let your leg rest OR do you want to take several weeks off later to heal from surgery ?"
All athletes end up with an injury at some point. You learn to take care of your body and learning to rest is part of a healthy lifestyle.
So, take a few days off. If you want to do something do some upper strength exercises while sitting in a chair or do some cardio. you WILL NOT derail any of your efforts at good health or weight loss because you can't exercise. Ultimately when it comes to weight loss or even weight gain, what matters most is what we eat. good nutrition is what takes the weight off and keeps it off. In short, you can't out run a bad diet with exercise. No matter what, you have to eat right first.