My son has a red Bloch that looks like a blood clot on the left corner of his eye. What could it be and how do we treat it?

Must be visualized. sounds like a small hyphema - broken blood vessel ( superficial)- usually resolves in 1-2 weeks.
Conjunctival bleed. This is almost certainly a subconjunctival (SCH) hemorrhage. It is not a hyphema which is bleeding inside the eye and could be serious. SCH occurs when a small vein in the conjunctival plexus seeps a little blood in response to coughing, sneezing, valsalva activity, local minor trauma and other benign events. These fade quickly and do not cause a threat to vision or eye health.