'tinier than' is correct and usable in written English.
You can use it when you want to compare two things and show that one is smaller than the other. For example: "The ant was tinier than the beetle."
His triangles are also tinier than usual.
My daughter studied this tiny newborn, and I recalled, "You were even tinier than he is".
First stop: President Obama, a little tinier than expected, with a too-perfect gleaming grin.
Audrey lies on Lisa's fourposter bed, nose bandaged, looking even tinier than usual.
How is it that snowflakes, tinier than tears, can carry such weight?
Nicola Adams is even tinier than you think she's going to be.
Before sewing add a couple of inches more than your size so it won't be to small or tiny than wanted.
But I've come to look upon the tiny, less-than-well-equipped kitchen as a delicious challenge.
Near Mr Berisha's home, in an even tinier settlement than Tropoje, a placard improbably proclaims the KLA's "headquarters".
Auriemma's Connecticut team plays Goliath to Louisville's David, perhaps an even tinier David than Michigan State was.
Not only was paleoanthropology itself a much tinier enterprise than it is today, but the sum total of hominid fossils known was hugely smaller.
