1 month old head circumference percentile went from 70th to 90th in 2 weeks. doctor says his head feels normal & looks normal so most likely it could be measurement differences since it was measured by 2 different people. is this normal or worrying?

You asked a separate question with the exact measurements at birth and at one month old. The current head circumference is still below the maximal circumference so you have nothing to worry.

If you are troubled by this issue and want to avoid the radiation of a CT scan, your doc can obtain a cranial ultrasound through the kids frontal soft spot. The study is adequate to detect hydrocephalus.