Hi. It is quite possible that your excessive crying may have precipitated a sinus infection. Here is how. Our tears are drained from a duct called as the lacrymal duct which can be seen on the medial side of the lower eyelids (near the bridge of the nose). This duct opens into the nose beneath the inferior turbinate. The lacrymal duct, due to its minute diameter, often collects dust and other secretions. In your case there may be an underlying irritant, allergen or infective material in the duct that got carried into the nasal cavity with the tears and into the sinuses precipitating an inflammatory response suggested by the congestion and an allergic response suggested by the sneezing and the post nasal drip. The green phlegm is indicative of a bacterial infection and you must consult an ENT specialist for a course of antibiotics, anti-inflammatory medications and perhaps saline nasal sprays to clean your sinuses.