At minor revision stage, I realized that a similar work exists in a Blog Post but not in a scientific journal

Don't panic and definitely don't withdraw your paper. A blog post isn't a peer-reviewed publication, and in the eyes of most journals, it doesn't constitute "prior art" that would invalidate your original contribution. Since you've added interval estimates and further analyses, your work provides the scientific rigor that the blog post lacks. The best move is to cite the blog post in your discussion section. Frame it as a "preliminary observation" or "informal analysis" that aligns with your more robust findings. By doing this, you show the reviewers and future readers that you're thorough and honest. The community generally views this as a sign of academic integrity rather than a weakness. It actually strengthens your paper by showing that your results are reproducible across different platforms, even if the original was just a blog. As a next step, write a brief paragraph explaining how your study builds upon the ideas mentioned in the post. Specifically, highlight that while the blog provided point estimates, your paper provides the necessary statistical confidence through interval estimates. Just be careful not to overstate the blog's importance. Treat it as a supporting data point, not a foundational theory. This keeps the focus on your peer-reviewed contribution while removing the stress of having "hidden" a known source.