A 45-year-old man with no significant past medical history presents with a 2-day history of colicky right loin pain radiating to the groin, associated with nausea and haematuria. He is afebrile. An urgent non-contrast CT KUB confirms a 4mm calculus in the right distal ureter. According to NICE NG118, what is the most appropriate initial management for presumed renal colic with a small stone likely to pass?