Conclusion
If your symptoms do not go away, worsen, or you experience any of the following symptoms [11], it is best to see a doctor: earache, ear drainage, shortness of breath, vomiting, wheezing, cough or sore throat that does not clear on its own, fever greater than 102 F (100.4 F in infants below three years), pain in your face or forehead coupled with the production of thick green or yellow mucus that lasts over a week, chest pain and confusion.
The best way to treat the flu is to stay indoors and rest. Drink plenty of fluids to stay dehydrated. If your symptoms are severe or too uncomfortable, you should take drugs to help alleviate them. Your illness should pass within two weeks. If it does not, see a doctor.
References:
[1] https://www.cdc.gov/flu/symptoms/symptoms.htm
[2] https://www.cdc.gov/flu/symptoms/coldflu.htm
[3] https://www.cdc.gov/flu/treatment/treatment.htm
[4] https://www.webmd.com/cold-and-flu/features/treating-flu-at-home
[5] https://www.cdc.gov/flu/treatment/treatment.htm
[6] https://www.cdc.gov/flu/treatment/treatment.htm
[7] https://www.mayoclinic.org/diseases-conditions/flu/diagnosis-treatment/drc-20351725
[8] https://my.clevelandclinic.org/health/diseases/13756–colds-and-flu-symptoms-treatment-prevention-when-to-call
[9] https://my.clevelandclinic.org/health/diseases/13756–colds-and-flu-symptoms-treatment-prevention-when-to-call
[10] https://www.webmd.com/cold-and-flu/flu-treatment
[11] https://www.webmd.com/cold-and-flu/coping-with-flu