Part of my inner cheek inside mouth [next to teeth] became slightly whiter ,then the surrounding skin, could this be something dangerous? mildly sore

Possible, not likely: Typically the white line areas are from chewing the cheek or drawing it in between the teeth as a nervous habit. Best to have it checked by your Dental Surgeon. Good Luck.

Several potential…: …causes comes to mind: irritation from biting/chewing the lining next to teeth; thrush/oral candidiasis from corticosteroids (Do you rinse your mouth well after Nasonex & inhaler use?); irritation from smoking; abnormal mucosal cells (dysplasia); & more. Since it is sore, reassure yourself with a trip to your dentist, who can better evaluate the lesion & advise what to do about it.