With the introduction of some Russian breeds of wild hogs into America's wild hog population. There has been some very large hogs come about. They go upwards to and over 1000 lbs and they are super aggressive. You better have something on you that will blow a tree down to stop one, unless you get that one shot of in the eye or ear. My dad butchered hogs as a kid using a .22 pistol. One shot, in the ear or eye. Never shoot one between the eyes, the hardness of the head and angle, usually only ricochets. As far as the self defense goes, you shoot one in that size range, self defense is probably not going to be doubted. But, yes, a hunting license just in case wouldn't be a bad idea. One final thing, don't think you will take it down and have it processed to fill you freezer. They taste terrible at that size. Never had one but have been told.
Just my two pennies chipped in on the subject.