Have a '14 A4 2.0T Quattro with 19" peelers which I put on back in March

Washed it this AM and noticed a slight sidewall bubble on the driver's front left tire

What's the risk of driving with a slight sidewall bubble?

I've heard in the past that if one tire on a Quattro needs to be replaced, all tires should be replaced. I know that one option is to have the new tire shaved to match the remaining 3 but is it required to replace all 4 at once? I'm guessing that these tires have around 12,000 mi or so.

Thanks in advance for your input

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