Looks to be anywhere from 4-7 months, but ifwould be better if we could see a photo of yor cham on your hand so we have a reference point.
do you know the gender?
He looks like my veiled and he is 3.5 months, but I think mine is a bit big for his age, so I would guess that your is around 4 months, but it would be easier to tell if there was something else in the photo for a size reference.