It's fine. Fill it in with some superglue if it bugs you. Once you start riding a little, you'll find if you go off replacing your tires after every little thing, you'll be out a huge amount of money.
General rule of thumb for me is if the casing is undamaged, I'll keep riding it. If the casing is damaged, I deal with it on a case to case basis depending on the extent of the damage. If it's a small tear or hole, I'll boot the tire and keep riding for a while. If it's a large hole, then I replace.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter