and so far have only done it the last 3 days for a 20 minute session each day, today i have woke up and my right knee is hurting? is this because im new to exercising or have i damaged it?

if you have excercised three days running it may be to much if your not used to it .if not is the seat on your bike the right hight ..i use to get pain in my knee but it was down to seat being adusted wrongly

You may just have overdone it a bit. It depends on how fit you were to start with. Try cutting down and do it one day then have a couple of days rest and see how it feels. Dont keep on cycling if it is hurting as this will make it worse. It may also help to do some warm up exercises before you cycle and some cool down exercises afterwards.

As it is a joint then you have probably damaged it or you had an underlying problem that has been aggravated, your thigh muscles would be hurting if you had over done it.

Get a real Bike and get some fresh air inside you

Its probably because you have down too much exercise. ou should do 20mins, miss a day, do 20mins etc, 3 or 4 times a week. Each time your exercising your body needs to repair the used muscles. Without time to repair you will not gain strength/fitness as well as resting and as a result hurt yourself..

It may very well be due to the fact you are new to exercise.It may also be due to incorrect saddle positioning. This is a common cause of knee pain in cyclists. There is a habit amongst those new to cycling and possibly exercise bikes as well to set the saddle too low. This is bio-mechanically inefficient and causes knee strain.As a starting point, sit on the bike and set either pedal in it's lowest position. Then let your leg hang completely naturaly, don't stretch it out or tense up. Ideally the ball of your foot should just be resting on top of the centre of the pedal, adjust the positioning to get as close as possible to this.