Need help encrypting a private key

I need to be able to encrypt a private key on my distributed program. I've read a few posts here, but I'm not sure they apply to my situation.

I have the ability to generate public keys based on the private key, and to confirm that public key against the private key through an API in the program. However, I want to make sure that my private key is as secure as possible. Obviously, storing it in a constant or an application setting is anything but secure, so I want to encrypt it somehow.

How should this be done?