2002 Vauxhall Astra tappet noise

Hi there im looking for help my astra has been making a loud tapping noise so I flushed the oil system and replaced oil and filter but seems louder, I removed the plastic cover and got access to the camshaft and it looks like one part of the shaft has worn down more than the other parts and I think this is where the noise is coming from, how do I get the camshaft out to replace and hopefully get rid of this noise?