How can I fix my mobile nokia 6230?

you can't it would have melted it'self into the plastic lense as it acts a bit like plastic modeling glue melts the plastic to weld two bits together. However try holding the phone face down and washing gently the lense with warm soapy water, the common way of removing superglue from fingers.
Obviously you need to hold it face down to prevent water getting into the phone. Dry it before uprighting it.

BOB
February 2005