Today I received a letter from google adsense team. I am very happy. but I am a few days ago already done ang request a new PIN. I became confused. Then I find information on google adsense help center. I am very lucky because my old PIN code can be used. The following information from google adsense
Question: Can I use my old PIN after requesting a new PIN?
answer: Yes. All replacement pins issued for your accounts will be exact duplicates of the original, so you can enter any of the pins that you receive, regardless of which one arrives first.
For Further information you can read here google support