What you are describing is something called a subconjunctival hemorrhage. Basically what this means is that getting 'clunked in the eye' caused a few small blood vessels located just under the white part of the eye to burst, allowing blood to escape. This looks terrible, because it shows up as bright red against the white part of the eye but, in essence, it is no different than a bruise
under the skin.
Most of the time a subconjunctival hemorrhage will eventually go away on its own and doesn't require any specific type of treatment. However, it would not be a bad idea to go see your primary care doctor
just to make sure that everything is alright, especially if you are having any other symptoms, such as severe pain, spreading of the area of bleeding
, or any visual disturbances.
Sometimes, when you get hit in the eye, you may have injuries to more sensitive structures of the eye, such as scratch on the surface of the cornea. These other injuries may require treatment, unlike the 'watch and wait' approach that a simple subconjunctival hemorrhage requires. Your doctor can take a quick look and rule all of these other things out for you!