Take it to discount tire and see if they can fix it
Discussion
What do I ask for? To fill the leak? What’s average price so I don’t get taken advantage of?
To find and patch the leak. I've never been charged for that tbh. If you don't have a discount tire nearby, maybe call wherever you bought the tires form or another tire shop. .
Can’t I do it myself? Is there better option?
It's unlikely that you could permanently fix it yourself. Have you found the leak? As long as it isn't in the sidewall, they could patch it. I've had a couple screws/nails in my tires that they fixed and I never had an issue again.
While yes, you can plug one your self, discount will fix it for free as long as it’s not in the sidewall. I do as much of my own maintenance as I can but I take my leaky tires to discount lol