Check injection

[Tigger84]

Hi, ive just bought a 2006 1.9dci cc karmann privelidge. All was fine on the drive home etc but now i have a spanner and error on the dash saying check injection and the engine runs very lumpy. Like i have to help it keep going by keeping my foot party on the accelerator until the car is up to temperature and then it settles down a bit but still idles rough. Any ideas where i should start investigating as i have 0 mechanical skills. I can check my tyres and fluids but thats about it