Android NFC Credit Card reader

At the outset let me say whilst I do understand programming - I use PhP I have no real knowledge of Android. I am looking to use a credit card in an access control application, say to a club or gym. The NFC device would read the card, but only capture the last 8 digits and no other information. There is therefore no possibility of misuse of the card or the details This would then be matched against the gym's database, where the cardholder's details had been previously stored with the cardholders permission and allow entry accordingly. I must stress that there is no payment processing and the full card number and the security code would not be captured or required.

There are existing apps that can read the card and display the number for example EMV Card Reader, NFC Reader, Credit Card Reader. Whilst all of these capture and/or display the 16 digit card number, I am unable to find where this is store on the android mobile phone and how to recover it.

Any advice or help with this application would be greatly appreciated