I also agree. I did that exact same thing on my first grow. I actually didn't repot it. I had enough room just to add more soil in the pot it was already in as it was sitting a bit deeper into the pot. If you have room, you could just add more soil on top of what you have up to the cotyledons. That is as I said if you have room for it in the pot it is in. If not, definitely re-pot now. Also you could always add a 1/4 tsp of "superthrive"(or a little less since it is so young) to the water you give it after re potting it will help the plant recover if there is shock or stress. Hope this helps.
Good luck,
Elway
elway07 Reviewed by elway07 on . what to do about tall seedlings? Anyways I have some 8 day old seedlings. They still only have 2 real leaves as of now. I made a mistake in the beginning by letting them strecth too much under a cfl. So now they are tall and lanky sorta. Anyways I dunno exactly what I should do if I should support the stems with a stick or to just let them grow on their own. None of them have fell over yet. I feal as if they are growing slowly due to being so tall. They are on 24 hour light schedule in a soilless mix called ProMix "BX" and are Rating: 5