Do it now, Gilly - phone for emergency advice first if you like, but I am sure they will tell you to go to A&E. This sounds like an infection that flares repeatedly a few days after it is sealed up each time. It is NOT draining - it is building up pressure and must be investigated and fixed straightaway.
If you leave it, it could become blood poisoning, which can be fatal! The emergency departments will be overworked and understaffed in a few days, with the Christmas alcohol poisonings and stupid accidents and so on. Going now gets it seen and treated in relative peace and quiet.