is it the phone lock code or the sim pin? if its the sim pin, you'd need to call your provider to get it unlocked. if its the phone, try a switch off and on again
does it say PIN code or Lock Code? if its lock code, the default is 12345 unless you've changed it of course. if all else fails, im not sure if your phone provider could help. but i could suggest you visit the nokia service centre to get it unlocked
PUK is for pin rather than lock. lock is phone based and not sim based, so the provider wont be much of a help, unless of course the provider provides the warranty