hello and welcome to HCM forum,
i would like to inform you that the white patch
which has developed on the cheek and the gum is most probably from the medicine applied on your tooth, i cannot assure if its a burn until checked clinically.
i do not know the reason behind the pain in your tooth, is it caries(decay) or due to infection in the gums.
i recommend you to use an antibacterial mouth rinse(twice/day) for 5 days,
also, you can apply Dologel-CT over the soft tissue
which is sore(apply with finger, massage
it for 1 minute and leave it for half an hour).
For the tooth ache
you will have to see your dentist
as he/she might prescribe antibiotics and painkillers.
i hope i answered your query,
i wish you good health.