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He is having headache and soar throat only four days history. It all goes in favor of upper respiratory tract
infection. This URTI also explains the dullness and gastritis
he has .
He should be taken care of by warm antiseptic gargles, some analgesic
. He may also be given some antibiotic if his throat is quite painful and red.
I don not think that this problem is related to his accident.
Hope he will be better with these advises.