I have had a mouth ulcer for 4 days. it is as big around as my thumb and started with me biting my cheek while sleeping. It is on the right side toward the back slightly higher than the midline. It is very sore and that whole side of my mouth hurts. The node under my jaw is very tender and I think the node in my neck is getting tender. I also have a sinus infection or whatever virus of the moment is in our house. We have been snowed in for over a week and can not get a doctor even on the phone. I have cefdiner and amoxicillin that were prescribed for what looked like a sinus infection but cleared up on its own ... so never had to take them. I feel like my mouth ulcer is infected and I should take some antibiotics. If so, which should I take since my options are limited by the weather.