Thanks for writing in to Healthcaremagic.
is caused by candidial (fungal) infection and cold
sores by virus Herpes Simplex
.Both of them can really be quite painful in children.Apply ice or cold compress on the lesion on the mouth and for inner lesions you need to apply antiviral
creams.Although the cold sore take around 10days to heal up by itself applying antiviral cream could heal it faster.
Give your baby bland or sweet food preferably liquids.If your baby seems to be having no oral intake and is getting dehydrated then it would be better if you take her in urgent care.If she is eating ,drinking and passing adequate urine then maybe you could wait till Monday.
Hope to have answered your query.