If the red lesion doesn't resolve in 2 weeks, seeing an oral surgeon is advised.
It could be a bite, could be oral cancer, could be an std. It could be another health condition. I wish I could be more specific but there are many possibilities. Go to an oral surgeon. If not satisfied, go to another oral surgeon.
Looks like a bite mark to me, but after a few weeks if it' not gone, have your dentist or doctor take a look. In the meanwhile, rinse with warm salt water to get it better, faster.
it was a bite i think (maybe during sleep). now okay.