gjbassist's hamstring tear brings up a good point: injuries are a matter of when, not if. I've been at it for coming up on two years and haven't been hurt too badly yet (a lot of what I study is about avoiding strains) but I once sprained my left knee and ankle simultaneously. The knee sprain wasn't severe but the ankle was and together, it was very painful.
You should also know that martial arts and self defense, though they overlap, are often not the same thing. Martial arts are disciplines that can take many years to learn and often have a sport element. Many are not very practical in actual combat. If your only concern is self defense, there are dedicated self defense classes to consider. These will be oriented towards practical matters that you might not get from a martial art and it won't take years to become proficient. This is why I asked exactly what your safety concerns are; it's easy to ask the wrong questions here.
You should also know that martial arts and self defense, though they overlap, are often not the same thing. Martial arts are disciplines that can take many years to learn and often have a sport element. Many are not very practical in actual combat. If your only concern is self defense, there are dedicated self defense classes to consider. These will be oriented towards practical matters that you might not get from a martial art and it won't take years to become proficient. This is why I asked exactly what your safety concerns are; it's easy to ask the wrong questions here.