I've never had angular cheilitis, mine involved my entire mouth. Mine occurred b/c I was using a new lip balm and I had an allergic reaction to it. Have you used anything new recently? I don't think it's anything serious, I did a brief search and it said it's common, a cause of angular cheilitis could be nutritional deficiency or infection. I would wait a little while and see if it goes away, if not see a dermatologist. Mine gave me meds to apply. Good luck!