I have never been a good runner and have started training for triathlons. Recently I have been pushing myself to train for my weakest part of the triathlon, the run. I felt like I lean to one side when I run. I just had my legs measured and found that my right leg is a whole ½ inch longer than my left leg, explaining the leaning and probably some of the pain; I had never noticed it before because my sport of choice has always been competitive swimming where I would have never noticed a difference in leg length. Does the difference in my leg length increase my chances of getting injured and if so is there anything I can do to help me run more efficiently and safely? As I said, I am training for triathlons so I split my time between the sports and only run two or three times a week (training for the 5K distance).
I'll let others comment on the amount of discrepancy. I think my memory is telling me that when you start talking 1/2" that's getting into the "no minor" category.
My word of caution is to, in essence, not go fixing a problem that isn't there. I've seen people (me included) get focused on making sure they're exactly even (shoe lifts, etc.) and I ended up making the problem worse. While the body is prone to injury in certain circumstances, it also is highly adaptable. So I'd only worry about it or investigate it if some injury pops it's head and you need to figure out the root cause. And even then, leg length discrepancy may be just one of quite a number of possible root causes.