Hi i have a pup which one eye is open & the other one is still closed 12 days old it looks okay the closed one can anyone advice please what to do.

It's not unusual for the eyes to open at different times, between 10 and 14 days; but of course if you're at all worried contact your vet.

Thank you Jeangenie that has put my mind at rest,if it has not opened by the time that the outhers have then i will ring the vets up thank you

Very common and varies greatly between breeds. I have had some open at 13 days and the odd litter at 16 days. Never any before 13 days.

My biggest worry on eyes opening was last year, when my Yorkie girl had 7 pups (huge litter for the breed.)  The first pup opened eyes on day 13, another 2 on day 14, and all the rest on day 15 - except one!  I was concerned to say the least.  On day 17 I had a vet appointment ( I had already had nightmares about him being blind, had no eyes etc...)   Obviously knew I shouldn't mess with the eyes myself.  There was no discharge, or indication that there was anything wrong with the eyes, I was just worried about the long delay.  I picked the pup up ready to get off to our appointment - looked at his face once more - he blinked both eyes, opened them wide ( I swear he said idiot), and he ended up being the frst pup to stand!  Shows you can only go by guidelines, there are no definites with dogs. 

Am I misreading this, I think the OP means that one of the pups eyes has opened and not the other???

Yes. It's not that unusual.

Yip I have had one that was 2 days apart. Just once though. The first one was quite early.