Is euthanasia the only option?

My dog is a fairly healthy 15 year old girl. She still interacts with us, loves eating and going outside, sometimes has restless nights, has arthritis which she gets shots for as treatment. but for the most part she is okay. the problem is about 2 years ago she developed a growth on her foot. the vets refused to amputate because her age makes it high-risk. it got larger and larger, and she would occasionally lick it. but it's gotten to the point she is obsessive. she licks her growth until there's no skin there and it's bleeding, we wrap her foot but within a few hours she has taken it off and again is licking it obsessively. we got her a medical boot as a barrier, but we can't keep it on too long at a time. All we can really do is push her face away from it when we catch her. The growth clearly makes her uncomfortable and in pain.My family loves her so so much but it's starting to make me feel very guilty, and i wonder if it's worth putting her out of this pain and misery.