What do you recommend for Canker sores (stomatitis aphthous)?

I got one recently (its been awhile) and its lasting a week so far. Very painful when i eat. I read on a TCM website that it has to do with heat in spleen and heart. And that you have to clear heat from heart and spleen and nourish yin. You think thats correct? If so what herbs would you recommend? Which ones should i stay away from?
thanks