Hi Ann,
Here I think this is the post your looking for...
http://www.stopsmokingcenter.net/support/viewmessages.aspx?topic=28122&forum=15
A small number of smokers do experience ulcers, however you should consult your doctor if it gets worse, bigger...
What you can do in addition to the advice given in the link is practice good oral hygiene. This will keep the sore from getting infected and causing you further problems. Avoid really spicy, sour or salty foods. Make sure what your eating isn't too hot or cold.
If it is really uncomfortable, ask your doctor about your options for pain relief. He/she is the best authority to give you advice on this subject as he/she is aware of your medical history.