lakshya so it works? That's great
There are settings for the icons in the admin panel, so that should work? If not, that's something you have to ask in the PWA thread: https://discuss.flarum.org/d/23219-progressive-web-app-and-push-notifications
I haven't explored all the settings yet, so I can't help you much right now. In fact, I don't know if you mean the notification icon or the app icon or which icon... Maybe it's the same as your forum's favicon?