Hi thanks for your question.
you have blister
in your mouth and pain in you in neck, when you stretch your neck or touch it.from the symptom it looks like that the blister you have inside your mouth has got supper added infection which has given rise to inflammation of sub mandibular lymph
nodes ,which gives you pain while stretching your neck and also when you touch it.
No PMS don't produce symptoms like that.
Get your self examined by a doctor ,who can tell you what this blister is?
Hope I answered your question.