Baby’s soft spot

Hello mamas. I have a 6 month old boy and a month ago I’ve noticed that his anterior fontanelle (soft spot) has become really small..I found it strange since it was more prominent the first few months. I brought it up at his 5 month appointment and the doctor said yes it’s small, but his head is growing normally. I was still concerned that it’s rapidly growing smaller, so they told me to come back in the beginning of December for a checkup. I’m a bit worried because It’s about the size of my finger tip now. Has anyone experienced something similar?