Hi.. Thanks for the query.. As per your complain the symptoms of drooping of mouth and difficulty in swallowing from the painful side along with difficulty in chewing due to lip biting is not appearing due to lip biting rather it is appearing due to disorders related with Facial nerve and is pointing towards Facial Nerve Palsy or Bell s Palsy.. As the facial nerve supplies the muscles of the face any disturbances in its functioning like compression by any artery, tumor etc, traumatic injury, viral infection etc can cause paralysis on the affected side.. I would suggest you to immediately consult an Oral Surgeon or a Neurophysician and get evaluated and a thorough clinical evaluation and investigations like x ray, MRI scan, Nerve conduction studies and Electomyography etc can help in diagnosis and treatment can be done accordingly.. As of now do warm compresses over the affected side.. The physician can advise you a course of steroids and if there is viral infiltration of the nerve anti viral medication can also be advised.. Hope this helps.. Regards.