You can pot them up in regular potting soil or the soil from your garden. I never sterilize the soil. If you do, you'll also destroy everything that's good for a plant (in nature nothing is sterilized!!).
I tried Hydrogen Peroxide and a lot of other things in my water, but nothing prevented mold for`100% when the plants are indoors. Indoors there is not enough circulation. But I never lost a plant because there was mould. I just take it away every week. The plants seem not to bother.
I always keep the left over seedlings for another 2 weeks, in case something goes wrong with the ones I transplanted.
Also-- commercial potting soils do not need sterilizing, they are already free of plant pathogens. I also agree with Jonna on the use of hydrogen peroxide. Save your money and spend your time watering correctly and you won't have to worry.