ちゃform is a little bit casual way to express feeling or some of the order.
mean, You have to go, don't you?
or I have to go, don't I?
But be careful.
1,If you want to say [行かなくちゃ？] to someone you want to let him go,mean,
you have to go, don't you?
2,If you say [行かなくちゃ] to your partner which mean
I have to go now.
○○しなくちゃ You can use this expression.
You suggest the activities for your partner or you want to let the person do the activities.