Hello again Ita and thanks for waiting,
I have worked out an answer for you, please read it through and see what you think, ... lets get started.
While I cannot diagnose this over the internet I have to say that any sudden onset swelling on the face area including the muzzle is typical of an allergic reaction in the dog. This is actually very common and is usually the result of an allergy to an insect bite but in your case it could well be down to the vaccines.
I am aware that many people treat this with the likes of benadryl. Here is a link to the use of benadryl in the dog including dose rates and contraindications etc. : LINK .
A usual dose rate would 1 mg per pound of your dog's bodyweight given twice a day, in your case that will be 8 mg twice a day orally.
As long as your dog is not deteriorating and is reasonably happy then you would be taking very few risks in giving Benadryl and then sitting things out until your normal vet is open rather than going to an ER vet as this situation is rarely dangerous. However if your dog deteriorates at all or other symptoms develop then you should play safe and see a vet ASAP.
I hope I have covered your question fully enough but if you would like further clarification or to talk things over a bit more then I will be on-line for the next hour or so and I will be more than pleased to continue working with you.