Positional Plagiocephaly This refers to the flattening of one side of the skull due to prolonged pressure on one spot, often due to the baby spending too much time lying on their back. This can lead to an alternate head position, where the infant prefers to turn their head to one side. This is commonly seen with the increased use of back sleeping.

Try lateral position while sleep, pls visit pediatrician once for examination

Is there any swelling on head, just make ur child sleep on side instead of of flat, position change during sleep can help