I have mouth sores and ulcers as I can't stop biting the skin inside my mouth, it's so sore how can I stop?

Ulcer in mouth. Keep in mind that any non healing ulcer in the mouth should be examined and possibly biopsied to rule out a malignancy (like cancer) particularly if you smoke/drink alcohol.
Anxiety? This could be a sign of anxiety. You should talk to your doctor. You could also wear a mouth guard, especially if you do this at night.
Sores in the mouth. You need to cosult a dentist. To find the solution. Use soft toothbrush, rise your mouth with listerine and see the dentist to prevent biting inside your mouth.