You may have developed a traumatic cyst--a fluid-filled sac brought on by biting. This isn't serious, but won't go away on its own. A dermatologist can diagnose this for you and probably treat it very simply if necessary using electrocautery. (Of course, it may not be a cyst, in which case medical treatment with creams and such may do the trick.)
Best.
Dr. Rockoff
That exact same thing happened to me a few months ago!! My doctor had no idea what it was. He even tested it for herpes to see if it was a cold sore. It wasn't and he couldn't tell me what it was. He put me on antibiotics though and it went away finally. Glad to know what it is called.