halfadevil wrote:
Yes it can, as it has nothing to do with the shape or tightness of the band, it is being caused from the watches sensors that measure you heartbeat.
No, there is nothing in the sensors (they are really just a type of light) that can cause pain in your arm.
There's a very straightforward explanation of how the sensor works here:
Your heart rate. What it means, and where on Apple Watch you’ll find it. - Apple Support