Tom,

There is no teaching on this topic or any obstacles to restoring your foreskin in and of itself.

Circumcision is not a Christian obligation and St. Paul goes through great length to argue this.

In fact he even has strong words to say for those who circumcise, although his context is a different one from the reason we do it today.

So as long as you have good motives for this (as in anything), it's OK to restore your foreskin.

Eric