Praise be to Allah.
You do not have to erase this software and redesign it from scratch.
Rather what you must do is get rid of an amount equal to the haram capital that you used to design this software. As for the profits, they are yours to keep, and there is nothing wrong with you benefiting from them after that.
But if this haram wealth was stolen or seized by force from others, then what you must do in that case is return the stolen capital to them, in addition to half of the current value of the software, and half of the profits that you acquired from it.
If you do not know the identity of the owners of the wealth that was stolen or seized by force, then you should give this amount of money in charity on their behalf.
This answer is a summary of what our shaykh, ‘Abd ar-Rahman al-Barrak (may Allah preserve him) told us.
And Allah knows best.