A 6-year-old child from a tribal village presents to the Primary Health Centre (PHC) with severe pneumonia (fast breathing, chest indrawing, and stridor). The PHC has oxygen concentrator and basic antibiotics but no paediatric ICU facility. The nearest Community Health Centre (CHC) is 25 km away and has a 24-hour emergency department with paediatric ICU. What is the most appropriate immediate next step?