Hi welcome to HealthcareMagic
Chewing the pan masala will not have any effect on the opening of the mouth, it will lead to ulcers on tongue, buccal mucosa, and staining of the teeth... but chewing pan for many years will cause thickening of tongue.. and Dysarthria
(speech disturbances).. you need to be clinically evaluated and examined.. other cause for not able to open mouth are, lock jaw., in case of tetanus
, painful angular stomatis, parotitis
etc.. consult an ENT specialist
he will guide you....