An infant's urine should be washed but does not invalidate Wudu'
I performed Wudu’ (ablution) for Salah (prayer), then I held a baby that stained my clothes with urine. I washed the spot stained with urine and offered Salah without repeating Wudu’. Is my prayer valid?
Your Salah is valid, because the urine of the baby that fell on your clothes does not invalidate Wudu’, and all you have to do is to wash the part stained with it.
May Allah grant us success. May peace and blessings be upon our Prophet, his family and Companions