Sinusitis and antibiotic advice?

I have had really bad sinusitis with lots of inflammed nerve pain which didn't go away on its own. I've been put on augmentin duo forte twice a day and the sinus nerve pain is much better but I have a sore mouth now. I am guessing its a side effect of the antibiotics and am unsure if I should keep taking them. I'm over half way through the course? Any help or advice would be appreciated.