Something of a whimsical thing as it's undoubtedly easier to just go and get a real thing, but hypothetically, can you use a Bards Performance of Creation (allowing you to create a nonmagical object, in this case a tiny one) and then use an artificers Magical Tinkering to imbue it with magic?

As far as I can see, the bards ability says you can make a nonmagical item that's medium or smaller (in this case, tiny) and doesn't say that this becomes magical. Magical Tinkering specifies it is allowed on non-magical items only, which the item would, in theory, be.

However, the bards item also glimmers and you hear music when you touch it, nd it disappears when another thing is made - but nothing explicitly states it's magical, and the only text I can see says you can make a non-magical object, meaning the object made is non-magical.

Further confusion to this; if you say the object is magical, then if you make a dagger, is the dagger magical? If not, can you magically tinker it?

I was certain in my head that there was some detail in Performance of Creation that says the object is overtly magical, but  I was mixing up in my head with Minor Conjuration from Conjuration Wizard, which does include language that the conjured items are considered magical, even though it's limited to mundane objects.

Performance of Creation does very explicitly use the term "non-magical", and although it lists magical effects tied to the object there's nothing that says the object is magical unto itself. "Specific beats general" comes into place here... despite the flavor and description implying that the object should be magical, the specific use of the term "non-magical" overrides those details.