You do not need to have a logo. You may have a blog without a logo, but the only thing that will distinguish it will be its name, so make it memorable.
If you want to build a logo for your blog, keep in mind that it will give it a distinct identity, and whatever you post on it may be transformed into branded photos that you can share on social media.
Because graphics are more popular online, your logo will aid in the promotion of your site. As a result, your blog logo design will not assist you to improve your search engine position. Quality material is required to rank highly; however, you may identify that content as yours by using your iconic logos in your blog.