The shell is still on the seed and if it has dried, it's probably gotten stuck.
You can try put a drop of water on it to maybe soften the membrane and shell to help it slip off, but might need a little more help and you run a big risk of damaging or killing the plant.
Keep your seeds damp until the shell comes off.
Planting too shallow can have it pop up and dry out before it's come out properly.
Some seeds just have a thick shell and struggle to split.