My 18 month old son scratched the sclera which is the white part of his eye he has a red spot and some red lines. half of is eye is red . what should ?

Subconjunctiva blood: It sounds like your son got a subconjunctival hemorrhage. This just means that a small blood vessel that lies within the conjunctiva broke and the blood is trapped under the conjunctiva which is a clear layer of tissue that lays over the sclera (white part of the eye). You should still have him see an eye doctor to confirm this and rule-out any further damage.It will last 7-14 days before clearing.

Observe: Your description sounds like a subconjunctival hemorrhage which will resolve over 1-2 weeks. See an eye doctor to be sure.