Prescribed amox/clav 875 2 times a day for 10 days. could only handle the side effects for 7 days. would that be good enough for sinus infection?

Sinus: By definition you have had an incomplete course of Abx. Best to be rechecked esp. if purulent discharge, Could use oxymetazoline spray every 4 hours for one week to decrease tissue swelling around sinus openings. Also saline nasal irrigations three times a day for one week. This is assuming you do not have chronic rhinosinusitis, polyps, smoker. These conditions will require much more treatment.