The urine of a male infant who is still breastfed and does not yet eat solid food is purified by dousing/sprinkling water over the spot (nadh) without needing to wash and wring it out, whereas a baby girl's urine must be washed like adult urine. Umm Qays bint Mihsan brought her infant son to the Prophet (peace be upon him); the boy urinated in his lap, so he called for water and sprinkled it over the place without washing it. This distinction is the view of Ahmad and al-Shafi'i based on the authentic texts; once the child begins eating ordinary food, the urine of both boy and girl is washed normally.
Evidence — the daleel
Sahih al-Bukhari 223 (Umm Qays bint Mihsan) ṢaḥīḥSunan Abi Dawud (narration of 'Ali: the girl's urine is washed and the boy's is sprinkled)
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.