They ripen after they've been picked. So, eventually, it will get ripe.
If you want to hasten the process, put it in a brown paper bag and store it at room temperature or even just slightly above (but not hot).
That will trap the gases released from the avocado and help speed up the ripening process.
2 to 5 days should do it. Check it. If it has a firm feel but gives a bit when you squeeze it, it's ripe.
To kick start it even more,
you could toss a banana in the bag. It gives off more gas, faster and will ripen it and the avocado that much quicker.