Hi welcome to healthcare magic ...
PUS anywhere needs to be drained . Secondly usually pus is secondary to bacterial infection and hence needs a course of antibiotics. For pain you can use NSAIDS like Ibuprofen
Hope you are sure its pus , because from what you say it seems its lymphadenopathy
, which is common secondary to any infection in the draining areas.
Lymphadenopathy means swelling of lymphnodes
, which are present on either sides of neck , just behind and below the jaw. Get a surgeons consultation , if you are sure its a pus i.e Abscess