Sore mouth causes anywhere from a mild to extreme cases of sores/blisters/scabs around the mouth area. Most of the time it is concentrated in the corners and the side of the mouth. However, young nursing kids can pass it to their dams while nursing and the udder/teats will breakout it scabs all around it. This can be painful and may cause the doe to stop nursing her kids until they are gone. So if your lactating doe does acquire sore mouth on the udder, just keep a close eye or her and her kids. Make sure they are getting enough food.
The sores can also show up inside the mouth which can cause lots of pain and discomfort. The tissues in the mouth can swell to unrecognizable sizes. In young kids, don't be suprised to see the gums swell up so much you cannot see their teeth. This is a severe case of sore mouth and great care must be taken to assure the kid is eating and drinking. This case would probably take 2-3 weeks to completely heal over. But as long as no infection starts there should be no lasting effects or any permanent damage to the kid.
There are a few different strains of sore mouth, some more severe than others. There is a vaccine available for sore mouth, it is a live virus. It gives the goat the disease and will create scabs. If you property does not have sore mouth in the soil I would strongly advise you not to give this vaccine, because you would be contaminating your ground. Sore mouth is hard to kill. It is contagious to people, so always wear gloves when dealing with the infected goat.

Up close & personal with Sore Mouth