I forgot my lock pattern

you'll have to reset the device most likely, but you'll need the volume buttons working, even if its just temporarily.

if youve worked on things before, order a volume button switch and hook it up to get into the bootloader/reset screen and wipe the device.

if you havent, take it to a shop, i wouldnt think theyd have that part on hand so it may be a few days to get parts in, and they can hook it up and reset it, or just fully replace the buttons.

if theres a google account tied to it though, theres a chance that you will still need to be able to provide the password associated with that google account after its reset to use it.