My little girl had this from about 3 months, we just left it it’s very common. It’s now growing back (she’s 5.5 months) as she’s sitting up more etc
Saw someone on another similar post suggesting silk cot sheets (like the pillows and hats to protect our hair) not sure if they are in line with safe sleep though!
My baby boy is the same, I was planning to leave it tbh and let it come back naturally. Wasn’t sure there was products to help the issue x