My baby is 10 wks, he often holds his thumbs btwn 1st& middle fingers should we b "teaching" not to?

No "teaching" needed. A normal, healthy 10 week-old baby who is using his first 2 fingers to grasp his thumb in either hand should stop doing it as he develops more, and starts holding other things. At routine baby check-ups at 1 month, 2 months, 3 months, 4 months, 6 months, etc... Parents should talk with the doctor about any such baby behaviors. The doctor can refer to a specialist if the baby seems abnormal.