I have a pain in my leg that I think may be muscle strain. What can I do that help it?

Rest. Strain is basically a muscular inflammation due to injury or irritation. As per therapy, ice/heat, rest, and antinflammatories can help. Sometimes your doctor can prescribe muscle relaxants if so needed.
Watch. Well, first off, you want to make sure it's nothing you need to see your doc for promptly. If there is swelling, visible vein, hot skin present, you need to run to your doc. If it is just the pain and you know you pulled it or twisted it, try to elevate it. Partial or, better off, total non-weightbearing (crutches) may be helfpul. Icing and compression are recommended as well. Ibu/tylenol +.