I would put a hold on the kick-boxing for now, and cut back on faster  running or climbing/hiking of any kind right now. Light jogging and  light walking should be no problem, and will keep the circulation up so  your hammies can heal. A mild case of hamstring strain can take a few  days to a few weeks, if you do not aggravate the condition further.

I  generally do enough speedwork during the year to cause nagging  hamstring pain. If I back off on the speedwork, and work on the  hamstrings directly with manual pressure, the pain recedes. Last year I  trained right up to a scheduled marathon with nagging hamstring pain  that would force me to shorten my stride during faster running. Even the  day before, on the way to my event, I had that pain. I massaged it with  one hand while driving (driving is especially hard on the right  hamstring), and ran a successful marathon the next day with no pain, one  of my fastest, and a boston qualifier. Temporary relief is possible, even within a relatively aggressive schedule.

When a nagging hamstring returned after really intense  speedwork lately, I was able to complete a 20 mile run last weekend  with only a couple twinges of pain in the hamstring (miles 9+16), and no  limping or after-effects. On balance, my hamstrings actually hurt less after that long slow run, even a couple days after when post-exercise  soreness is typically at its worst, and no pain at all as I write this.  Yet, just two miles of tough running can irrititate my hamstrings if I  push too hard. The difference is the intensity level. One heals, the  other hurts. Another important point is to avoid sitting directly on the  part of the hamstring that is hurting, or anywhere that impedes  circulation. After a number of years, I am getting pretty good at  balancing intensity with recovery, so please take my experience as an  important lesson for handling hamstring strain.

Meanwhile,  you can work on your own as successfully as I have, by learning how to  self-massage the hammies. Some use a foam roller for this, but at least  initially, I recommend using your hands to locate the trouble spots in  the hamstring, because you can probably feel them with your fingers. The  spots that need work are usually a bit firmer or rubbery, and feel  different from the rest of the muscle in that they do not appear to be  relaxed tissue. Often, there will be more pain when you press there,  even a lot of pain when pressed. Let your fingers slowly sink into these  spots (sitting on raised fingers works easier), so that the pain and  tension feel slightly relieved by this pressure. As the circulation  slows in the compressed tissue, the tension should slowly melt away with  it. This technique is called "ischemic compression," and puts tense  tissue temporarily to sleep. THe response to the pressure will be  increased blood flow when the pressure is removed. You want to release  the pressure after several seconds to allow the tissue to "breathe,"  which will reduce the chance of cramping or further damage. The idea is  to increase vasodilation by forcing the muscle to adapt to  vasoconstriction. Increased blood flow + less intense exercise = faster  recovery. Good luck!