I didn't, didn't think that the game would allow me to ignore items needed for a boss I could still access. Tried playing this again but it didn't exactly go well as I couldn't even pass the nose boss, no idea how I did it on the first try earlier as now it was incredibly hard. The attacks are way too fast and you can't know where they're coming from in advance so it seems very rng-based if you win it or not.
Don't know if you could do that boss later more easily though because it doesn't give you anything that seems mandatory at that point.