Wa'alaikum assalam! Pusat baby yang timbul biasanya umbilical hernia je, yang mana otot perut belum fully close lagi, sangat common especially dalam first few months, don't worry. Mostly akan settle on its own by age 1-2 tahun, tapi sebaiknya check with your baby's doctor lang to confirm and make sure everything okay, especially if pusat baby jadi besar-besar or baby look uncomfortable.