and verify that it is in the hope that it is only some particle of dust that is on the dial and not a problem with the dial itself, if it were a particle on the dial the questions would be how did it get there, that is more difficult to explain It could even be a piece of S-luminova that came off at some point, but that can only be known by opening and analyzing the dial., If you find out, tell us what it was and how you solved it.
cheers