Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns.
As per your complain a white blister inside the mouth of your son that has a red surrounding area seems like an Apthous ulcer or
canker sore or a traumatic ulcer caused by chewing or biting the lip and does not seems like
Cold sore as cold sores appear as
fluid filled blisters commonly present over the lips..
I would suggest you to consult a Pedodontist or an Oral Physician and get evaluated and in case if it is an apthous ulcer he can advise him to apply a numbing gel but to be precise to apply only over the ulcer..
You can be advised to apply a steroid ointment to reduce inflammation..
Vitamin B complex in syrup form can be given..
Tylenol can be advised to reduced pain..
Applying cold compress or ice over it can relieve..
Give him
soft diet , more of fluids..
Avoid spicy and citrus foods..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.