There are two reasons: First, if you get angry, you can eat gunpowder at will (Sanhuang tablets, Niuhuang Jiedu tablets or oatmeal for clearing fire).
If pustules appear around a good tooth and often appear, it means that this tooth may have dental caries where you can't see it. Bacteria invade the pulp, causing inflammation inside the pulp. Externally, it is those boils. If the teeth are blackened, it means that the tooth nerve has been necrotic. However, if this is the case, you may feel toothache in the process.
In addition, there may be wisdom teeth. When I have wisdom teeth, there is a pustule on my gums.
I suggest you go to a regular hospital to see a dentist as soon as possible.