Use the "Low Pass Filter" (see: https://manual.audacityteam.org/man/low ... ilter.html)
However, that will probably make the recording sound dull.
Piezo pickups often over-emphasize frequencies around 2000 Hz (2 kHz). If you use "Plot Spectrum" (https://manual.audacityteam.org/man/plot_spectrum.html) you will probably see a pronounced bump, spike or bunch of spikes around 2 kHz (may be at a higher frequency depending on the pickup).
Make a note of where that peak occurs, then try the Filter Curve EQ effect to reduce those frequencies. (See: https://manual.audacityteam.org/man/fil ... ve_eq.html).
[Unfortunately Hamm542 was a spammer and has been permanently banned. Leaving this reply as it may be useful for future users.]