Thanks for your query.
It could be a meningocele
They are the congenital spinal defects noticed In new born.
Does the swelling Increase In size on crying or any straining activities?
since In the above two mentioned conditions It is an Important sign that Is noticed.
Kindly take your kid to a Pediatrician
Initially or directly to a Pediatric surgeon If available.
Hope I have answered your query.
I will be available for your followup queries if any.
Wishing you good health.