Not to take away from the advice above, however a creaking or cracking sound is not natural (duh) and would recommend seeing an orthopedist for X-rays and evaluation. Until then I would not stand in the pedals or do any activity that promotes said sounds. Hopefully it is nothing to be concerned about, but would be a shame to ignore it and have it turn into something you really have to be concerned about.
My wife had a knee replacement (cyclist, runner, skier) when the cartilage was ground down to nothing. She was a compulsive exerciser and didn’t stop until there was no return. It was no small surgery.
At at least a medical opinion is good insurance.
__________________
Road 🚴🏾♂️ & Mountain 🚵🏾♂️