Tire sidewall quarter size bubble/bulge

No question - replace the tyre

 

Definitely replace. Had the same problem on my normal car (usually caused by hitting a pothole). You're at higher risk of a blowout for sure.

 

With a radial, it's much a risk of blowout, but a sudden flat after hitting a speed bump, pothole, etc. at some highly inconvenient location(been there).

Those bulges tend to spread over time until a weak spot in the rubber is encountered, then they pop.

 

any defect like this can cause extreme heat build up inside a tire and result in sudden and catastrophic failure of the tire, usually at speed (ask me how I know). Do not try and put a radial tube inside...big mistake (ask me how I know).

If there is a lot of tread on the tire, take it to the dealer you bought it from and see what they can do or see if they can write you a little note that the tire is defective ...then if you are very lucky and persistant you make get a pro rata credit on a new tire...(I did all the above and got zippo..but you might do better)

 

The tire is shot and needs to be replaced. It could last a day or a year, but you will be at risk of tire failure every time you drive it, with risk of loss of control and/or expensive rim damage at the least. You don't say what kind of tire it is and how old. The mfr. may replace it, but if it's an original tire, not likely after so many years. Unless you look for a good used one of the same type/mfr, you may end up replacing both fronts (assuming it's front..) with non-matching tires to rears (acceptable, but may alter handling, depending on tire selection), or have to by a complete new set so that they all match.