My 9 year old finished his antibiotic a week ago for strep. his gland and tonsil on the right side are still swollen but not as much when first diagno?

This is common: The abx rx is designed to prevent the secondary problems (heart, kidney, brain) of untreated disease & speed recovcery of the initial infection. The gland & tonsil swelling may take several weeks to settle down after primary treatment. 8&9 yo kids tend to have larger tonsils/body size than at any other age so some swelling may persist.

How diagnosed?: And what was the treatment? On rare occasions there may be bacteria present in the back of the throat which produce enzymes that prevent the antibiotic from working on the strep. Tonsils are lymphatic tissues which help to fight infection, and may take time to reduce in size once the infection resolves. If they do not slowly resolve, see your doctor again.