Yeah I would second that . Get a Bike fit is the best solution . Unlikely we will be able to diagnose the issue online , all we could do is throw you all the things to look at . And Almost always Knee is not the problem its caused by something else .
Is the pain , front (anterior) , rear (posterior) , side (Medial//Laterl) or just overworking stress as knees will always be one of the first areas to tell you when you work just a bit too hard.
anterior and posterior Knee issues first thing to check would be
Check your crank length is suitable for your size . Cranks too long will cause bad angles and that will cause ultimately rear (but sometimes front) knee problems . You can search online for information on appropriate crank length for your size . Standard bikes very often come with longer cranks than are ideal.
Are your cleats properly aligned , another common issue across all knee issues . Unless you have a reason to make do otherwise ( advised so ) make sure your clear alignment is pretty straight…
Saddle height and horizontal adjustment is another often cause of knee , both posterior and anterior ( more the former normally) , how to check Watch this for some pointers . How To Set Your Road Bike's Saddle Height - Tips For Getting Your Saddle Position Right - YouTube
Medial and Lateral Issues
Get someone to look at your pedal action and see if you are toe in or toe out to any degree . Pedal “float” can help here .Assuming you use clipless pedals that is . Some pedals are better than others for adjusting float , speedplay are particularly good but an expensive sort of option if its only on a whim.
Cleat adjustment too and often do cause issues here , common bike fit change most people get is here as a result
One other perhaps unexpected but common cause of Knee pain is weak core strength .Cyclists we concentrate of our quads and stuff but often neglect core and thats a sure fire way to get knee issues
as a gymnast I would be surprised if it is this .
Finally make sure you are not just overdoing it to quickly , turbo training allows us to work extremely hard , much harder than we would do normally , so listen to your body too . I am suer with a bit of tweaking though with some assistance you will get it sorted . Almost all cyclists get knee issues it comes with the territory.