Hi..
I have gone through your query and will try my level best to solve your problem..
As you are using a prefabricated mouth guard there are chances that it is not well fitted or there can be some sharp or rough elevations over the tissue surface of the night guard which when rubs against the gums above font teeth can cause
injury and inflammation leading to irritation and swelling..
You should stop using the night guard and should first of all
consult a dentist and get the mouth guard and your gums checked..
In case of sharp points trimming of the same has to be done..
If not fitting well get a custom made night guard fabricated in a dental office as per your proper size..
As of now you can apply a numbing gel containing Lignocaine to relieve pain and soreness..
If there is pain OTC painkillers like
Ibuprofen can be taken..
Avoid wearing the night guard till the gums heal well..
Do cool water rinses to reduce inflammation..
Hope this information helps..
Thanks and regards..
Dr.Honey Nandwani Arora..