I resolved it last year with the trick mentioned somewhere:
# Make your phone stand up on its own
# Then push it so it falls forward or backwards flat on the table (it should make a big bang on your table).
# The force of the gravity will make that small dust particle move, in my case it moved out of the frame
# If still there, repeat the step 1-3 again.
#
Haven't had issues since then, hope it helps guys.