Sounds to me like a quads tear, perhaps of rectus femoris which is the central quad. It is used a lot when kicking a ball but ot so much when cycling as the hip is rather flexed making that muscle become more slack. When you straighten the left and contract your quads in standing can you feel any void or bump in the muscle. If so this would indicate a tear. A good physio should be able to assess the probability and it can be confirmed via ultrasound scan or Wikipedia reference-linkMRI. I would ask someone at least to send you for that type of investigation. Some physio's may even be able to scan it for you