No, your account has not been hacked. What probably happened is that someone with a user ID similar to yours made a mistake typing their user ID, and entered yours instead. The requirement for the security code prevents them from signing in to your account, since you got the code and they didn't. The code is sent before they can actually sign in. You can just ignore the code.
The other possibility is that someone intentionally tried to sign in to your account. But the security code requirement still stopped them from actually signing in.
