There is no way to heal it unless you have a Splash Potion of Healing/Regeneration. Although there is a rumor that you can heal it by feeding it fish after you tame it.
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A cat in Minecraft is called an ocelot.
you heal it by getting porkchop and left clicking on it. you should see its tail go up if successful
Jungle Biome
its a animal that if you tame it, it will turn in to a cat that helps you just like if you tamed a wolf on minecraft.
If you mean Minecraft Pocket Edition, you tap and hold on the screen with food in your hand. Certain foods heal more than others.