My 3yr old came home from daycare with very red eyes. no discharge in his eyes. should i be worried about pink eye?

Possibly: It is conjunctivitis and needs treatment.

Yes: "pinkeye", or conjunctivitis, is a very common problem in daycare centers and school. It is often highly contagious, and spreads by touching. There does not have to be discharge for this to be conjunctivitis. Many case are viral, and self limited (go away by themselves) but an exam with a doctor, pediatrician or ophthalmologist, is advised to confirm the diagnosis and see if treatment is required.