My 17 Year Old Son Is Experiencing Nausea And Fatigue

My 17 year old son is experiencing nausea and fatigue going on day 3. He was diagnosed with influenza A on 1/19 and prescribed the generic form of Tamiflu which he finished taking on 1/24. Nausea started 1/28. He was also diagnosed with mono in Oct 2016 and had his tonsils removed 1/3/17. Should I seek treatment for his nausea (he vomited once on the first day)