Don't panic. Low purity primarily means you're getting less active ingredient than you think, so your dose is effectively lower. The degradation products in peptides are usually not toxic — they're typically inactive fragments. But "usually" isn't "always," and without characterization of those impurities, we can't say for certain.
The bigger concern is what it says about the pharmacy's quality systems. If they're releasing product at 82% but labeling 98%, either their testing is inaccurate or they're falsifying COAs. Neither is acceptable.