What to do with a slightly under-ripe winter squash?

A friend gave me a butternut squash, but it's slightly under-ripe (not sure if you can see in the photo, but it's a bit green still) and there is a dent/cut in the neck so it needs to get used before that spot goes bad.  I'm not sure how being under-ripe will affect a winter squash... is it better to bake and puree for a pie or something that will get plenty of other flavor added as opposed to cubing and roasting as a savory side? Any other other tips or recipe ideas appreciated. I don't often cook with butternut, but I don't want it to go to waste!

Slightly underripe butternut types work well for baking or as a soup puree with stronger flavors like curry.  You have it right about adding flavor and not using the squash as a stand-alone veg on the plate. Really underripe butternut types can be used like a summer squash with peels and seeds left in. They are good in stir frys or as pieces in a veggie soup. I call those fall squash as they're what's left immature at the end of the season and get harvested before frost.  You can pull immature little fruits from other "winter" squash early in the season and use them instead of summer squash or zukes. We do this with Delicata and have stopped growing a dedicated variety of summer squash. Underripe fruits will not store as well as a fully mature fruit so should be used sooner rather than later.

some good options from Larissa!

here’s the thread where i asked this question a month or so ago:
https://permies.com/t/190215

I have read that butternut squash can be ripened off the off the vine. But you have to put them in sunlight.

For me, this has been tricky. I picked the squash because it was getting too cold. So how do I put them in sunlight? I don't have a greenhouse.  

Mine usually ripen ok if almost mature, even without sunlight IF they had plenty of minerals while growing. We use the slightly green ones  in stir fry with peppers, carrots and onions.   If I have broccoli I throw some of that in.  Anything we don’t eat is relished by pigs, goats, chickens or wildlife.  Even our dog will sometimes grab a piece away from the pigs and eat it.   Hard rind butternut, and I prefer the long neck as they have more “meat” on them compared to seed cavity, store a year after harvest usually.  No need to refrigerate, just keep off the floor to avoid moisture condensation and turn once in a while to check for any rotten spots.  If you find any, cut out the good portion and use immediately.  I seldom plant any, what comes up in the compost pile is usually enough.  We just throw cattle panels around the patch to keep goats and pigs out.