Hi..
Can understand your concern.
As per your complain a large painful swelling under the chin can occur as a result of infection or obstruction of the
salivary gland duct of the submental salivary gland which is one of the major salivary gland leading to pain and swelling ..
As you have experienced a traumatic
injury there are high chances that the infection has occurred in the salivary gland which must have travelled via the gland ducts causing gradual infection in the gland leading to inflammation and swelling..
It can also be due to obstruction of the gland duct caused by the crystalline stones formed into the ducts by minerals present in the saliva causing obstruction in salivary flow which then gets pooled into the gland causing swelling and over distension causes pain..
There can also be formation of non cancerous tumours and cysts in the gland following injury..
I would suggest you to consult an oral pathologist and get evaluated for the cause of the swelling and treatment will be planned accordingly..
Hope your query is solved..
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Thanks and regards..
Dr.Honey Nandwani Arora.