The leaves of peppers and other vegetable starts will curl under for many reasons including lack of water, sunburn from adjusting to full sun from partial sun at the nursery, herbicide drift from a weed killing chemical or an underground pest such as moles or voles causing root damage. Too much fertilize and fungal leaf infections can also cause leaf curl. In many cases the plant will survive these attacks and grow through the damage. Keep the soil moist and see what happens. If you send a photo I may be able to give a more accurate diagnosis. Keep growing, Marianne Binetti