I didn't create a private key for my bitcoin address and am unable to do anything with these coins. How do I resolve this issue?
In order to properly create a Bitcoin address, you need to create it from a private key. If you just start from the middle of address generation - say a public key or a result of a hash, you are not guaranteed to have a private key that can be associated with that address. In order to recover a private key that was never used to create an address would require you to brute force all the private keys, which at the moment is computationally impossible (might be more possible in 50+ years). This is in place to ensure that nobody can steal your coins.
If you are using Bitcoin honestly, however, you should find your private keys stored it wallet.dat in the Bitcoin data directory, or in case of using eWallets - online.
You haven't stated from where you obtained the Bitcoin address in the first place.
It didn't come from the same wallet in Blockchain.info/wallet because Blockchain.info/wallet won't let you watch one of your own addresses.
If the address is from your Bitcoin.org client (i.e., Bitcoin-Qt), then you simply spend from the Bitcoin.org client and not from Blockchain.info/wallet.
If the address is from another EWallet on Blockchain.info, simply log into the correct wallet and spend from that.
If the address is from an EWallet on some other service, e.g., on Mt. Gox, then you will need to go there to withdraw any funds that you've received.
Hopefully you can remember from which wallet or EWallet service you obtained the Bitcoin address from originally.