Want to second the dentist suggestion. My brother has some sort of condition with his gum tissues - they're not infected, but for whatever reason, there is an overgrowth of tissue. Apparently you can choose to have it surgically removed, but he hasn't wanted to go through this. Certain things will cause his gums to swell and hurt - I think that the two biggies for him are pistachios and intact pieces of beef - he'll eat a hamburger, but strips of beef in a chinese entree will make his gums hurt.