Imho, it doesn't look like the typical
picit ('thumb impression')... (maybe a baby's thumb, perhaps)

.
Hmmm...I do love your piece, though... so sweet. My type of blade with nice 'greneng' works,
pendongkok (hilt ring),
hulu (hilt) and
sarung (sheath). Should you ever wanted to let it go... do remember me...
However, I wonder what's the purpose of such a 'dent' at the base of the blade? Is it on one side or on both sides of the blade?
Clearer close-up pictures might help to see the structure of that area.