How can I protect my creation and address manager's unethical behavior

As part of the AI initiative at my organization, I recently developed a computer application on my own. The application proved to be beneficial to multiple departments and won first place in the monthly competition. Unfortunately, my manager had no role in the creation process and, in fact, created obstacles to delay or dismiss its progress. After the win, he made demeaning remarks and failed to acknowledge it as my individual effort. Last week, I learned from a team member that during a call with a director, my manager took credit for my creation, claiming it was his idea. This has severely impacted my confidence, and I see it as a breach of trust and an unethical act to claim someone else’s work. I’m seeking advice on how to safeguard my creation and possibly initiate legal action to hold my manager accountable for these unethical practices. He has displayed toxic behavior, and I can provide further details to higher management if necessary.