you can clean his mouth with cotton wool in mild antiseptics like TCP and you can apply bonjela cream for soothing effects as first aid on your way to the hospital for proper diagnosis and treatment.

WE NEED TO KNOW WHAT TYPE OF SORE AND WHY the baby has the sores in the mouth in the first place!!! It could be an illness, Vitamin deficiency, Micronutrient deficiency and so many other possibilities. I will encourage you to see a MEDICAL DOCTOR first for proper evaluation, diagnosis and treatment.

Dear mum, the sore in your baby's mouth could be as a result of the illness.
However, kindly take the baby back to the hospital for treatment of sore development.