Brownish pigmentation buccal mucosa.

I have this brownish pigmentation majorly on the right side of my inner cheek, i showed it to dentist they said its physiological pigmentation, i have applied kenacort, caziQ for almost a month now it reduces the redness but when i stop it comes back again, first there will be redness which feels sour, after that it turns into brownish/darkish colour, initially it started in my right bm, but now it is starting in my left mucosa as well. Right now i have been diagnosed with k. Pneumonia in my sputum culture majorly sensitive to almost all the antibiotics, and getting treated. I have other symptoms as cough, i have esionophils 10.5%. Apart from that no other symptoms, i have taken lycostar, rebagen for a week too, why is this pigmentation happening? Is it bec of the pneumonia infection? Should I be worrying about that? I don't smoke or eat tobacco, no exposure to chemical fumes too. Please help. Attached image of 1. Left bm, 2. Right bm