The stock sank this week despite a strong Q2 report.Chipotle Mexican Grill (CMG 3.14%) reported its second-quarter results late Wednesday afternoon, and in after-hours trading, its stock surged. But on the earnings call, the company warned of near-term margin pressures, and on Thursday, the market erased the stock's initial gains and it kept falling. Chipotle is now down by more than 25% from its recent high, though it's up about 11% on the year.Has that recent sell-off created a good buying opportunity?Str ...