HI, thanks for using healthcare magic
The fact that he was given an antibiotic to treat his throat infection
implies that the doctor believed that it was bacterial rather than viral. Though viral pharyngitis
is more common, children can sometimes become infected by a bacteria.
In upper respiratory tract
infections and other viral illnesses , pain around the eyes is common and it is possible that this is what he is experiencing.
The redness could be because he is tired as you stated.
If he had history of trauma to his eye, then you would need to have his eyes evaluated as soon as possible.
Since he is tired, you can consider letting him rest for a bit, give him some analgesia such as paracetamol
,for the sore throat
and headache, it would also help the fever.
You can see how he is after he's had some rest.
If you are still unsure or uncomfortable with how he is then you should take him back to be checked out.
I hope this helps