2004 megane 166 authentique?

is this a very serious problem and must i have it fixed immediately - took the car in to the dealers to check for faults on the computer as i had just bought it and it needed the 90 000km service which i had done privately - dealers quote was too expensive - the only fault which showed up was CAMSHAFT SENSOR LIGHT came on. they have given me a quote of 2k to fix, and i'm broke - please help, would hate for something bad to happen for not sorting it out soon.