R.J.
Its indicative that he has strep throat.
As long as it responds to Tylenol/ibuprofen, its fine. If he's maxed out on Tylenol & Ibuprofen (taken both within the past 3 hours) ... And is 103 & climbing... Take him in immediately. But a low grade fever is just his body fighting the infection.
Id only be concerned (all thing being equal / aka no other health issues) if it were a stubborn fever (see above, not responding to meds), or lasts longer than 10 days. Although, I would call my sons Doctor on Tuesday just to update them, as there are R-Strep strains that may need different antibiotics / are resistant to the antibiotics he's already on.