DELL XPS 9570 ventilator noise question. Could use a few insights

Hi guys.

I think there is something wrong with the fan of my Dell XPS 9570.
Which is called an XPS 15 right?

For some time the fan is making a lot of noise when it's blowing at a low RPM.
It's not blowing excessively loud or fast as some other complaints describe.
Except for when I'm playing a video game but that's normal.
It usually occurs when I've just booted the laptop and when I'm doing medium tasks like browsing with chrome or watching a YouTube video.
The sound occurs with or without a secondary screen attached.

The sound is best described as humming maybe a bit scraping.
I've already checked if there is excess dust in the fans or a hair because that could explain the noise.

Is there a fix for this? I've never did anything weird with my laptop and it's usually stationary on my desk.

Thank you for your time. It's a great thing this community exists.

Also: did checking the fans (opening the back panel) cancel my warranty?