I have a tiny bubble on my front tire and I'm sure I'll need it replaced.

First, are the tires old or fairly new because you could still have a warranty on them so it would be covered at a prorated rate.

Most OE tires do not have a Tire Warranty. Some manufacturers will offer a 1 time good grace adjustment but it isn't guaranteed. In answer to your question, yes you need to get the tire replaced. The bubble is a slight perforation in the inner liner of the tire and the air is leaking into the sidewall. This will only get bigger and at some point will blow out on you. For your own safety, change that out. Since this is an original equipment tire, these do tend to be more pricey. Depending on your location, a reasonable price is anywhere from $275-$295 installed.