Thank you for the information.
By analyzing the history it seems that he is having flu or viral infection.
Viral infection is common to cause fever, gastrointestinal symptoms.
It usually continues for 3-5 days , can take longer also.
Symptomatic treatment like tylenol for temperature
, plenty of fluid etc. is sufficient.
Sometimes secondary bacterial infection can occur .
But pain around umbilicus needs some evaluation by doctor right now.Appendicitis
can have low grade fever along with start of abdominal pain
around umbilicus though nasal congestion and blood shot eyes goes against the possibility of appendicitis.
Still in this age group I would suggest to consult his doctor to be on safe side.
I hope everything will come out as normal.
Please ask if you need any clarification.