I applied too much urea by mistake, how do I save the crop?

Excess urea usually shows exactly what you describe: very dark green, soft, overly leafy growth that tends to flop or lodge, delayed maturity, and often more pest and disease pressure on the lush tissue. You cannot remove nitrogen that is already in the soil, but you can manage the situation. First, stop adding any more nitrogen to that patch, including foliar nitrogen sprays. Do not let the soil stay waterlogged; managed irrigation can help leach some excess nitrogen down past the root zone, but do not flood to the point of drowning the roots. Watch closely for lodging and for pests and diseases that thrive on soft growth, and be ready to support or manage those. Make sure other nutrients like potassium are adequate, since balanced nutrition helps the plant build stronger stems rather than just soft leaves. In future, split your nitrogen into measured doses and mark which strips you have already covered so you do not double up. For corrective steps specific to your crop and stage, check with your local KVK, and base future doses on your Soil Health Card or soil test without over-applying.