Had first fire of the year. Noticed that there was what looked like a soot spot on glass. When stove cooled I cleaned glass and spot not coming out. Felt inside of glass and could not feel anything. Felt outside of glass and could just barely feel a slight bump outwards (bump is immeasurable, only running finger over it shows smooth bump outwards). It almost seems like the dark spot is inside of the glass. Tried taking pic but couldn’t get a good one. Stove about 6 years old. I’ll keep an eye on it, but is this common?