When it is closed and they are ready to take the stitches out put Neosporin on it to lessen the scarring so that you will be able to bend your thumb normally without it pulling and feeling stiff. Put it on every day.
We did this with my granddaughter when she fell off her bike and had stitches in her face. As a matter of fact we put the neosporin on from the getgo and she does not have any trace of scarring.