Yeah you can just take it into an Apple Store. It'll be under warranty with Apple.
For your future reference, you can verify warranty & warranty expiration date by entering the device's serial number into this website: https://checkcoverage.apple.com/gb/en/
It does not matter if you opened or not they will still give you a new one. If it is in stock. I only use Apple stores for service even though I've purchased somewhere else.