In some cases yes, but generally the acid concentrations in urine aren't strong enough to fully neutralise the sting, but with some stings the acid can prevent the release of further venom into the victim.
I dont think peeing on a jelly fish will stop it stinging you. What you 'should' mean is IF it stings me and the sting gets p'd on then it releaves the symptoms.
Welcome! This is the strangest question yet! As far as I know, peeing on a jellyfish doesn't help, but peeing on a sting neutralizes the toxin. Hope that helps.