Can I prevent team members from sharing my board?

Yes. You can change members' permissions at any point.

How to Change Member's Permissions / Remove Members

1. Open the Boards app, enter your board and tap on the share icon +👤
2. Tap the 3 dots
3. Tap View Members
4. Tap on the email you want to change permissions
5. Change permission or remove from the board
6. Get a confirmation message 👌🏼

Check out this article (iOS/Android/Desktop) to learn how to do it.