My Guinea Pig has a growth/lump on the centre of his back. It has a scab in the centre and in my opinion looks like it is filled with something, as if I squeezed it (which I don't plan on doing) something would come out. This is especially due to the scab in the middle seeming like it goes deep, as if it goes deep within the bump rather than sitting on top. Has anyone had anything similar, or know what it is? I'm a student and really can't afford anything extreme. My parents have suggested using hydrogen peroxide on it.