Slight gap between screen and housing

I have an apple watch 4 for a month now. When I first got it I saw a slight gap between the display and the housing, but I thought it's no big deal at first. Now I can see dust is starting to build up and I'm concerned it will get inside the watch. The gap is big enough to easily slip a piece of paper between the screen and the casing. I'm scared of using my watch while swimming, which is one of the main reasons I bought it for. The gap is only on the side with the crown. I've searched online and found some other discussions on this and people say this is normal. Should I be concerned?

Thank you