Pain in Chondromalacia patellae is more when the knee is flexed. Driving a bike may exacerbate the condition. I would suggest you start with physiotherapy as quadriceps strengthening helps a lot. Also while riding the bike on coming to a standstill you plant your leg on the ground and it puts a lot of stress across the knee, more so if you're driving a heavy bike. If you are diagnosed with Chondromalacia I would suggest refraining from riding bike for too long.