While it is not impossible for a twenty year old to have an oral cancer, the likelihood is small. First, you know that the original tissue change was from a mechanical source (chewing trauma), and not disease. It could be that in your sleep you have again bitten the still remaining spot and not known it, making it appear to be a continuous, non-healing event, even though it is not. The fact that it has some white coloration to it, is probably just from the abrasion. True leukoplakias can be rather large and have a variegated appearance, and do not general associate themselves with areas of trauma. The tissue is frequently smooth and undamaged. In some smokers leucoplakias the tissue can be rough from the hyperkeratinosis. Second, you have none of the other risk factors for oral cancer. An indentation in the tissues of your tonsil, if it is not obviously a sore, is not red or white, and otherwise has a normal appearance, is unlikely to be cancer either. But you are doing the prudent thing, and that is having a pair of trained eyes give you an informed opinion.