The gemstone scene and all the elements surrounding it were indeed laden with hidden metaphors, many of which have been discussed here already.
I also saw it as the questioning or reevaluating of what a person considers precious. For Arjun it is a competition to best Karna and bring back a gemstone like the one Urvi gave him. It is precious to him because of her belief in him and because of the affection with which she gave him this present. He is eternally hopeful of winning a place in her heart, and for the male pride, what better way than to beat his now biggest rival in the race to bring her another gemstone?
For Karna, it is about making amends and being fair. He does not know of the importance of the gemstone in Urvi and Arjun's lives and the implications of it being destroyed during a competition. He has no greed or drive for acquiring wealth, nor does he think about competing for Urvi's affection. For him it is about restoring the balance in Urvi's life for damaging something that had personal value to her, even though it was an unintentional side-effect of the match, if you like. Despite his very recent rags to riches ascension to the throne of Ang, he knows of but does not care at all about the material value of the gemstone.
For Urvi, it is the trigger for her to begin to gradually question the importance of material goods and eventually her set of beliefs. She has seen luxury and experienced utmost comfort all her life. The gemstone was supposed to have been indestructible by just anybody, yet it had been, so easily. She is now curious and maybe even skeptical about the original claim regarding the stone, and has also realized that this Karna is not just anybody. I suspect there will be more incidents and scenes where her belief system will be challenged and she will be drawn even more to Karna's personality, but for now it's just sparks.
Finally, of course, on a subconscious (or conscious) level, the damaged stone and the demand for reparation gives her a good excuse to interact with Karna. 😉