[X] Apologize and offer compensation. -[X] Mina apologizes to the creature in its language, stating something to the effect of "We didn't realize this was your home/garden/nest." Then explain that we cannot spare the time to tend the fungus until it regrows. -[X] We'll offer the creature a steel dagger to aid it in its work and to defend itself if necessary (along with suitable instructions on how to maintain the blade), and invite it to join us for a meal. If it finds our foodstuffs palatable, we'll promise that when we return this way we will try to bring more food for it.
[X] Put on the snake oil vendor hat
-[X] "We apologize, fair one! We did never intend to cause any harm here, yet we have clearly failed! I am afraid that in our ignorance in these matters we would cause more harm than good. Yet, we have some repute as explorers and problem fixers both!"
--[X] "Tell us, fair one, is any creature other than us affecting your task? Are these plants in need of nutrients we could bring? We have access to settlements nearby, and they need not to know that we are bringing these things to you."