What causes recurring inflamed sore mouth corners and what can i do to make it better?

Angular Cheilitis: Angular Stomatitis or Chelitis describe inflammation and infection of the corners of the mouth. It is caused when excess saliva builds up at the corners of the mouth and dries, causing an initial irritation. Further licking of the lips worsens the problem and fungal infections can easily take hold. Talk to a Dr about a topical antifungal which will kill the infection and allow the area to heal.

May be Canker Sore : Usually ,some people get Canker sore during Winter.See your Dentist to rule out it is not Herpes. One thing is important that you should avoid touching the area to prevent spread of infection because it is Viral in nature. Get plenty of rest , reduce stress and get good sleep .