By using this technique tonight and 5 times tomorrow (with about 5 mL of water per nostril), you should already see a good improvement in his secretions and possible pink eye (possibly caused by too much mucus in his nose coming up to his eyes).
If in 2 days nothing improves in the eyes, I recommend seeing an optometrist or doctor.
To reduce irritation under the nose, simply put Vaseline™ on the skin.