I have a 2887 MQ5 thinkpad IBM Laptop, One of my key on the board was broken so I attached an external keyboa?

I have a 2887 MQ5 thinkpad IBM Laptop, One of my key on the board was broken so I attached an external keyboard with the help of usb port. Now the broken key is repaired and when I started using the inbuilt keyboard some of the keys when pressed gives a different input than those imprinted on the keys.What should I do?