I got an oral cancer screening done about a month ago now the roof of my mouth is white could cancer pop up that fast it does not scrape off so idk?

It might/depends,,,: At your age you shouldn't get oral cancer. This usually presents in a person's 50s. However as tobacco use, especially chewing tobacco is a very significant risk factor, young persons like yourself can get it if there is very heavy use. Also, there is a chance of cancer from hpv if one engages in oral sex and it can appear in young people. So do check-ups, stop chewing tobacco, and stay safe.

Anything is Possible: Just like any harmful disease or condition, it has to start at some time. It's always possible that such a time is right after you've had an examination. Any oral ulcer, lesion, or sore which does not heal within 3 weeks should be checked. Always assume it's cancer until proven otherwise. Don't mess around with any oral lesions which don't spontaneously heal. Get it checked and know for sure.