I do not think you ruined your salve. There are many herbal infusions and decoctions made with boiling water that have strong medicinal qualities. What oil and herbs did you blend together?

As long as the oil did not boil it should be fine. When the oil boil it will no longer be able to extract the medicinal properties, however if you saw no sign of boiling it should be fine. a better approach for next time if you are not using a root-herb as the herb in question would be to warm the oil, place it in a jar with the herb and then put it in a warm place out of direct sunlight and let it is sit for a few weeks while shaking it several times during that period, much like you would do with a tincture. I've found this to be a "safer" way so you're not worried about boiling the oil and ruining the infusion.

if it smells burnt, it's burnt. if not, use it. a safer way to infuse oils so they don't burn....put the oil and herb into a tightly sealed mason jar and put the jar into the slow cooker for infusing. this prevents the heat directly contacting the oil. you can also purchase an extension cord containing an inline thermostat for use with your slow cooker, to regulate temperature more exactly.