Rigging a character made in Unity

Within Unity I made a custom "3D Stick Figure" character made from capsule and sphere meshes. I'm now at the point where I need to rig my character, but I have no knowledge of Blender, 3D Max, or Maya. I've exported my custom character from Unity as a .obj file, but it won't let me open it in Blender nor Mixamo. What should I do now to rig my character? Am I doing something wrong? Do I HAVE to learn Blender and recreate my character there??