It seems you're doing great now and I think you already understand the concept of Bitcoin and how it will work.  As you have said above, your nephew said that he/she likes Bitcoin, which means, your nephew probably already knows or has a little idea about Bitcoin and that is the reason why he/she requested that valuable stuff from you.

Just a friendly reminder, remember that anyone who will hold the private key will be the new owner of your Bitcoin.  If you want to hand over the private key to your nephew, just make sure it is safe and should not be saved in any online third party or any device that could be hacked.  Valuable things like this are always prone to scam.