Sorry to hear that your son has a sore throat
. Normally pharyngitis (sore throat) is a viral illness
that runs its course in 7-10 days. However, if it progresses long than that, or if the symptoms are particularly bad, then perhaps it truly is a bacterial infection ("strep throat").
In order to accurately diagnose him as actually having "strep", he would need to get a rapid strep test done. This is a test that is done using a swab in the back of the throat which then is send for an assay that will detect if there is streptococcus present. This is a relatively fast test, but it isn't 100% accurate. Meaning that some of the time strep is actually there, and it doesn't detect it. Although more commonly the patient has been exposed to strep in the past, and now they have strep living in their throat in very small numbers, so the test may actually be positive, but the strep isn't the pathogenic bacteria in that particular case.
Thus the test results need to be interpreted in the setting of a good history and physical exam. While any ENT worth their weight would never turn you away for bringing your son in with a sore throat, an urgent care clinic should be well equipped to handle this problem. They will likely do a rapid strep test there. Hope this helps. Best of luck.