When changing your babies diaper you do need to and should wipe your baby after changing a pee diaper.
Although if you're using disposable diapers they are great at absorbing the pee there can be small amounts or pee or urine on the babies skin.
So it's a good idea to use some baby wipes or wet washcloth to wipe the baby down at least a little bit to clean any potential pee from their skin.
Also there could be some sweat on them that could make them smell and could give them irritation and a rash.
I've always wiped my babies bottoms after pee and also for a boy wipe their penis down some too with a baby wipe as the penis is very sensitive.
I forgot to do that a few times and my baby boys penis got red and got an irritation and some red bumps.
After wiping him down after every pee diaper change he no longer got that rash on his penis.
So it's always best to wipe the babies bottom after pee to keep them clean.
If the baby is wearing cloth diapers then you should always be wiping the baby after pee as cloth diapers don't wick the pee away from the babies skin as good as disposable diapers.
Also be sure to change the diaper every 2 to 3 hours or when it's full and avoid leaving the baby or toddler in a wet diaper too long.
If they poop the diaper then change the poop diaper as soon as you notice as poop is faster at giving the baby or toddler a diaper rash.