iPad screen inside got dust

If within your warranty period, you may be able to have the problem resolved at no cost. Conversely, outside of warranty, a repair will be expensive.

If you have benefit of an active AppleCare+ plan, you will have cover for faults and accidental damage beyond warranty. Being an insurance product, a claim made under AppleCare+ will attract a small excess/deductible fee.

If dust is visible within the screen - and it bothers you - you would be best advised to visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to offer assistance and you can explore available options for remedy:

Genius Bar Reservation and Apple Support Options - Apple

I would just ignore it. If you can't really ignore it, you can ask a third-party to try to get it out (which will void the warranty) or get your screen replaced by apple

I don't really use an iPad, but I just know from experience