Self-discipline is important and not just on that matter.
I'm not perfect, but I can give you some tips I tried.
1. Limitation. The more you expose yourself to the source of your problem, the more you will be consumed by it. Reduce the amount of time you spend looking at it.
2. TikTok has some real privacy issues and is probably spyware. Uninstall it or use it sensibly on another device;
3. Short videos are the worst type of video for someone with ADHD. Try to watch longer videos about topics you enjoy.
4. If you are on a PC, install the Unhook extension (for Chromium-based browsers and Mozilla, I think). It will unhook your youtube from any distraction you want. --> I use it to hide the home feed, live chat, shorts, etc... you can even hide comments.
5. If you're using your phone, I think there's an option to limit your app usage. You can also just hide your phone and go do something else for a few minutes and then come back.
6. Find a hobby. Don't just watch these short videos, try other things and focus on them. You can even do this on your PC or phone. On your PC, look for quizzes, read some short stories, find new search engines and explore the hidden parts of the web. Play some games, experiment with different software (like Google Earth or Stellarium). Use MS Paint and draw something, then post it on spacehey or somewhere and see what people think. I don't know... just some suggestions.
I hope this has helped in some way.