It seems that you have imported the keys into current gpg instance and haven't updated trust of the key. You can use
gpg --edit-key [email protected]
gpg> trust
gpg> save
to set trust of your imported key to ultimate trust. Please keep in mind that you should give this trust level only in special cases and your own key is one of them.
Basic PGP principal as for this is key signing in meaning of you meeting with other people verifying their identity and signing their keys as you have verified their identity. With setting partial trust to these people you will trust other people they met and verified If certain conditions are met as for example two separate chains of trust. This create web of trust which then allows you to trust keyes of people you want to talk to because they were verified by someone who has direct chain to you. The error you are getting means that gpg doesn't have any of these chains and it is warning you that you might not be talking to the person who is mentioned in the uid.