Thanks for sharing your concern.
what do you think is the cause of his cheek swelling?is it just the bruise
or the underlying tooth is involved?
swelling of cheek indicates,trauma to tooth and supporting structures. I would suggest you to visit your dentist
first regarding this,a vitality test for the concerned tooth will be carried out and then based upon the level of fracture
of tooth (if any),treatment can be undertaken.
later you can inquire about your other decayed tooth too,if adequate mouth opening is there and child is cooperative then superficial fillings( if any)can be carried out in the same sitting else you will have to visit later for that.
His first priority should be the involved tooth and its suitable treatment.
hope it helps.