Hi
It could be oral lichen planus.
I have a touch of it on my cheek on the inside of my mouth.
I had a biopsy years ago to confirm it.
I'm actually under the specialist division at my local dental hospital. They keep check of it. Once every 12 months.
My only irritating thing about it is, is that, that side of my mouth can get quite dry and sore, so I use bonjela on it occasionally, or a salt water rinse, the dentist is quite happy with that.
Xx