I bought an brand new OEM Grand Cherokee hood from a seller on ebay/instagram. He's seems to be a pretty reputable seller in the challenger/charger world. I received the hood in good condition but noticed this on the very front of the hood. What do you guys think? Should I be worried? I apologize if this is in the wrong section.

Looks like something touched the black paint while it was still wet. I wouldn't worry about it; there's always some bit of prep to do with replacement parts even brand new ones...

What did the seller say it was?.............

I have seen a Lot of corrosion on Aluminum under Paint over the years and Ya That does kinda Look like corrosion under the paint but Its not. That's Just a spot that Touched the Paint when it was wet still.
You could Just hit it with some Scotchbrite or 400 Sand paper to clean it off t see the metal it has to be re-primed any way.