Don't support the seedling. Giving it support now will only encourage it to continue to grow foliage and roots and not build any solid stem. By the time you flower, the thing will topple over for sure. Put a little wind on her to encourage stem growth.
stem support is in mho a negative action. a light breeze will strengthen that stem. As of right now I have a seedling doing the exact same thing due to some mulch rolling over it lol.whoops. So like others I have had it will eventually head upwards. nature gives you your answers go look at the trees not all started straight but look at the results. trust the plant.
if there is wind or a fan you are fine....but if it is long and weak...i would probably repot it and bury it up to the first set of leaves and the wind/fan will keep it strong fro now on.