hello and welcome to HCM forum,
according to the history presented by i cannot provide you with an exact diagnosis as your oral cavity needs to be checked clinically first.
you have not mentioned which premolar is it(1st or 2nd, upper or lower).
i assume that a pocket present with respect to the premolar is responsible for the pus and foul smell.
i would suggest you to visit your dentist
so that x-ray can be clicked to rule out the cause ,
presence of periodontal pocket
adjacent to the tooth can severe the tooth , therefore kindly visit the dentist soon.
i would recommend, warm saline rinses(3-4times/day), until you visit a dentist.
i wish you good health.