What is the right course of action?

Because you have a STOP sign, you have the strictest “give way” duty at this junction. That means you must first stop completely at the stop line (not just slow down). Only after stopping are you allowed to roll forward to get a better view, but you still must not enter the intersection until it is safe.

After stopping, you must give way to all traffic on the cross road, from both directions, including buses and cyclists. In this situation, both the bus coming from ahead and the cyclist approaching from the left are on the priority road relative to you, so you must wait for them before turning.

Rule of thumb for similar questions: STOP sign = always stop at the stop line first, then yield to everyone on the road you’re entering (cars, buses, bikes, etc.). Only go when the entire maneuver can be completed without forcing others to brake or change course.