My mouth is painful, when I chew i'll be biting the wall of my mouth and also red spot on the hard palate just behind front teeth. What could this be?

Bite might be off. It could be ulcer from trauma. Did you eat or drink something hot. If your biting the wall of you mouth, its your bite, is it normal or something new. If the red spots don't go away in 3-5 days, see a dentist to check hope this helps.
See the dentist. Sometimes you can be chewing your cheek in your sleep without realizing it your dentist needs to rule out any sharp places on your teeth maybe a night guard will help.