Please provide some pictures of effected area n proper history like from how many days he is having pain, which tooth is effected etc
Next Steps
(-) For Proper help you need to consult a doctor or video consult
(-) Till then can take painkiller, but always remember painkillers only subside pain temporary.
(-) Brush twice a day
(-)Warm saline water rinses
(-) Avoid eating anything hard from that area
Health Tips
Best way to diagnose a problem is to consult a doctor before pain aggravate.