Well, the wikipedia you trust so much has the following thing on this matter
Ghori led two regiments in an attack on the centre, where Ghori met Govinda Raja in personal combat. Govinda Raja, mounted on an elephant, lost his front teeth to Ghori's lance. As the battle continued, Ghori's army, exhausted in face of the persistent Rajput attacks and out of water, fled leaving their general Ghori as a prisoner in Chauhan's hands. Ghori was brought in chains to Pithoragarh, Prithviraj's capital, where he begged his victor for mercy and release. Prithviraj's ministers advised him against pardoning the aggressor but the chivalrous and valiant Prithviraj thought otherwise and respectfully released the vanquished Ghori. This which was a decision he would later come to regret. Muhammad Ghori started to regroup his forces again to defeat Chauhan the next year.
Prithivi pardoned Ghauri that time and should have killed him.