As he is older now- the crying and acting hurt technique may not be so effective. So I would use timeout.
Have him on a house line- the moment his gets OTT say "ah! ah!" or "that's enough" and lead him swiftly (but don't drag) out of the room into another room. Shut the door with the lead trapped in the door so you are holding it on the other side and the dog is in the other room. Leave him there for 20 seconds.
The message to him is: Nipping= No attention - no play

Timeout helped alot when my border collie was a pup

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