I believe you are referring to what's commonly called "lie bumps" (mothers used to tell children that you get 'em when you tell a lie), or transient lingual papillitis, which is irritation or inflammation of one of the tastebuds. This can be caused by direct trauma, such as by biting, rubbing, or scraping a taste bud, or by eating foods that irritate the area (acidic, sour, or foods you're sensitive or allergic to), or even gastrointestinal upsets, stress, or menstruation. Medical science hasn't really found a definite cause for these occasional sores, but the above are the most likely culprits. Either way, lie bumps tend to go away on their own without treatment within a matter of days. If it's particularly painful, you can use ice to numb it, or over the counter anesthetic creams, such as oragel. Also, over the counter meds such as OraBase or Zilactin can be applied, and act as a sort of bandage that protects the tastebud from further irritation as it heals.

I hope this helps!