Hi A Couple Days Ago I Was Hit In The

Hi a couple days ago i was hit in the mouth playing sports. Didnt think much of it didnt see any noticeable abrasions. The next day there happens to be a really small cut on the inside of my lower lip. Not on my lip but inside my mouth about a cm or two from my bottom lip. Doesnt hurt ive got canker sores so i took lysine. Next day it has gotten smaller with a white film over it. Cant even really see it but can feel it there. Is this a cut, cold sore, or canker sore? If it is a cold sore is it still really contageous at this state?