Use an absorben cloth to wipe up any wet urine from the surface, A diaper also works great for absorbing the most urine. Then wash the area off with a damp cloth and some vinegar to remove as much urine as possible. Next spray with an odor-removing bacteria and enzyme killer. If the smell remains, try this (but test in a small hidden area first). Then make a mixture of hydrogen peroxide(diluted to about 3%), a few squirts of regular dish soap, and a little baking soad. Apply it to the area wipe up. If the smell is still there, you are probably going to have to replace the hardwood as it most likely has speed into the wood and subfloor.