It sounds like you have developed a canker sore in the spot that was hit with the toothbrush. Have you ever had one of these? I get them periodically. They can be caused by trauma, such as with a toothbrush, biting your lip or cheek, or a sharp piece of food.
It will go away on its own, and it's painful, but nothing to worry about
. There are OTC medicines if it is really bothering you, but I usually just leave them alone.
I hope you feel better soon,
S.C.
http://en.wikipedia.org/wiki/Aphthous_ulcer