You can cook frozen meat, but the question is, do you want to? Here’s why I generally don’t advice it—although it can be safe to do so.
As the meat thaws, it gives off a lot of moisture, which then gets mixed into the pot with your flavorings and dilutes them. Perhaps more importantly, when you cook meat from its frozen state, you have to cook it about one and a half times longer, and in that process, the proteins are likely to toughen. It is best to avoid subjecting meat to extreme changes in temperature.
For more tips on using frozen foods, see Easy Freezer Meals.