Lynne is right speak to you OS. But know that definately there is the chance that the tear could get larger and cause problems. In the long run left alone it could cause osteo arthritis to develop within the joint.
My Dad had a meniscus tear and bakers cyst drained in April. He is 54 years old, and was back playing hockey 4 weeks post op. Arthroscopic surgery, while being surgery carries it's risks...is not as invasive as an open procedure. My dad had little post operative pain and went to physio for only 4 weeks and was like new.

So Surgery is scarry, but it might be the best thing. AFterall you can't stop bike riding for the rest of your life..it's too fun.
Take care and good luck with your decision
Linds