I'm confused about the hole from the stem. Do you have a picture? If it's mature, just place it on a counter and wait a few days until it's soft to the touch.
Commercial guys pick them when they're hard so they package well and don't bruise. They will ripen within 2 weeks that way. But you're not a commercial guy so you shouldn't use that practice. The larger cherimoya in my picture above was hard when it was harvested but had a little give.
This seedling cherimoya is NOT ripe! Notice how green it is. Small too.

Below, is a picture of the same seedling cherimoya picked while it was firm but easily separated from the tree. This is 2 MONTHS later. Look at the color on the left. The right is a bit from the sun.


This is what it looked like 4 days later and was completely ripe and delicious.