Brief Answer:
Clean the eye as advised and observe

Detailed Answer:
Hello

Thanks for asking on this platform

I can understand your concern.
I won't get overly worried for single episode of white discharge in an otherwise normal child where there is no associated symptom like stickiness, redness or swelling.
This white discharge can be thick mucus which can be there due to transient obstruction of duct connecting between eye and nose.
I would suggest you to clean the eye gently from inside out with help of sterile cotton.
Observe closely and please consult your pediatrician if you notice persistent discharge or any associated abnormality like redness, swelling, itching etc.

I hope this helps.
Please let me know if you have any more questions.
Regards

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