Recently My AdSense Account Was Limited due to infringement of copyright in my blog which is all about mp3 file sharing

From what you wrote here, your blog contains music files which you do not own the copyright to or have the permission to use/publish on your blog.

The copyright owners of these music files reported you for using their creative works (posting it on your blog) without their permission. This consequently got your account limited.

The solution to this is not to get copyright protection for your blog. As a matter of fact, your blog (the blog address) cannot be protected by copyright as it doesn't fall within the items eligible for copyright protection in Nigeria. (I assume you're a Nigerian). Copyright protection only exists for the contents/posts on your blog (if you are the original creator of those contents).

What you should do from now on is to avoid posting copyrighted contents on your blog without first obtaining the permission of the copyright owner.

Like I said earlier, your blog by itself cannot be protected by copyright but the contents on your blog can, provided they are your original work and not someone else's.

I hope you understand my little explanation.