4yo son has a red line, not whole eye on left side x 2 days. isn't complaining about it hurting. no pink eye exposure and no gooping.

See below: A subconjunctival hemorrhage occurs when a tiny blood vessel breaks just underneath the clear surface of your eye (conjunctiva). It's usually a harmless condition that disappears within one or two weeks. It often occurs without any obvious harm to your eye, or it may be the result of a strong sneeze or cough that caused a blood vessel to break. You don't need any specific treatment.