Does covering 21-23km per day as a beginner hurt your knees? I’m 29 years old and I have bought a hybrid bike 5 days back. I’m a beginner in this field and last time when I rode a bike was 15 years back. From last 5 days I’m covering 21 to 23km in approx 1 hour and 15 minutes with an elevation of around 250-300m. I want to ask that can it hurt my knees if i ride daily with this same scenario or I will get use to of it? Please note that i’m coming in this field straight out of couch.

Secondly, I’m 5’8” and I’m riding 17 inches bike. Is it perfect for my height?
If you are going from a level of inactivity to  21 to 23km a day, yes, you may experience some aches and pains. As you get fitter and more used to the activity these issues may go away. If issues persist see a doctor.

Something you should do is check your saddle height and fore-aft position.

A commonly used 'rule of thumb' for setting saddle seat height is to sit on the bike wearing the shoes you ride in, put your heel on the pedal, you leg should be just straight.

For setting saddle fore-aft position, sitting on the bike with the cranks flat, foot on the pedal in normal position, your kneecap should be vertically above the pedal axle.