If Animal urine and feces are not removed properly, they will often react with carpet dyes leaving a permanent stain.
Professional help is advised.
Continue using only water to rid the blood from area. The wax will soften and attract to the heat thus becoming absorbed into the clean towel. Change towels often to properly absorb the wax. Do not overheat as some synthetic fibers within carpets have a low melting point. Any remaining residue can be removed with dry cleaning fluid.