Cycling has the misconception of being a "painful" sport, where pain and discomfort are an expected part of riding a bike. While there is an element of physical adaptation to cycling to tolerate the unique bendy, narrow posture needed to sit on a bike, cycling does not need to be painful. Those completely new to cycling may experience some adaptive discomfort related to sit bone conditioning and muscle strengthening, however, this should be proportional to the amount of riding and not a limiting factor of riding.
In my experience, common symptoms that warrant professional bike positioning as soon as possible are:
Hand pain and numbness
Knee pain, especially if it is sharp and is present after riding
Foot numbness
Low back pain
Neck and shoulder pain
A feeling that you are fighting the bike positionally. (The bike should be positioned to support and let pedaling feel intuitive!)
If addressed proactively, all of these symptoms usually resolve within 2 weeks after proper bike positioning. The longer one "rides through" with symptoms, the more likely the symptoms will evolve into an overuse or compression injury and require further professional intervention (like physical therapy) to resolve.
As much as I love helping people as a physical therapist, I'd rather you use your time to ride your bike without pain instead of needing physical therapy. Proactive bike positioning helps ensure you get to enjoy cycling focused on your goals rather then goals focused on pain-reduction and injury management.