The greatest risk of this is sore formation, thickening of skin due to callus and infection. As infection, callus and sores can be disfiguring and debilitating this is a formidable problem. However, most issues come from the deeper skin being broken.
Morsicatio buccarum et labiorum
In some individuals habitual cheek and lip biting becomes a fixed
neurosis. Pieces of oral mucosa are actually torn free from the
surface, producing a distinctive clinical appearance termed morsicatio
buccarum et labiorum.
This disorder though probably not what your looking for us what extreme cases can turn into.
Oral Frictional Hyperkeratosis
Most patients with frictional keratosis are free of symptoms, with the
exception of those with aggressive cheek and lip biting habits. In
some individuals who repeatedly traumatize the tissues, tenderness,
swelling, and a burning sensation may be presenting symptoms. Patients
with persistent cheek and lip biting habits tend to have increased
stress and psychologic disorders. A patient may notice a thickening or
roughness of the involved mucosal site, or frictional keratosis may be
discovered as an incidental finding during a routine oral examination.
The risk of cancer from this seems low, but consulting a doctor or dentist would be the best course of action.