I'd wait for more than 3-4 nodes, but you could do it now if you wanted... just be a bit gentler. It has fewer roots to hold it down, etc... The key is bending it before the apical meristem (trunk) gets too hard to manipulate in that way. As long as it isn't woody, you are fine... likely have more than 2 weeks in that picture, i bet.. but each strain varies a bit. I have one that gets super hard stems very quickly. I have to becareful and do that one earlier.
First, think about where it is bending before doing it or mounting any tie-downs or stakes in ground etc etc..
Look at the growth. The nodes alternate 90-degrees each new growth. You want to bend it down between that 90-degree split so that each side of plant can grow vertically easily. That's the first step -- think it through and plan accordingly.
now, when you bend it, you can slightly bend between finger and thumb -- don't feel any crushing inside.. if you do ease up... small amount is no probelm it will heal. You can bend liek this in a few spots near the bottom to create a better arch to horizontal that doesn't damage the plant.
Any limb below that bend will be trash and you should just cut it off now.
so, it's been loosely worked and bent in a specific direction you choose based on growth of the plant. Now, you can use any nuber of ways to hold it in place. I use fabric pots, so i can staple some soft twine (thick so it doens't cut plant) in a loop where plent is bent woard. I use that adjustable loop (slips through staple, but enough to hold young plant) over the top of the plant to hold it down. I will also use a stake (paperclip - u-shape) to stake down the middle of the plant so it doesn't arch too much.
You want it to be farily level for best results. Nodes that are equal in height get equal amount of resources and will grow evenly. If anything grows tall, bend it down to keep that growth spread out. don't do anything crazy to get it perfectly horizontal... it's a goal, not a requirement.. don't do anything damaging to accomplish it. it's an impossible goal to reach.
Initially it seems like you slowed it down,but in reality it is growing all over, so it's harder to see. It is logrithmic growth, though so it will speed up very quickly.
Bend any branches upward if it can be useful (some may try to escape to side, but you can force it up to light with shorter path). Even tie those to do so until they grow into that shape. If anything is buried and has to grow a long horizontal lenght to get to light, it's safe to prune those off too as they won't ever amount to anything useful.
So, most things are growing out and away from teh trunk, so you can bend a few of the lower limbs straight up to fill the middle. If you don't get them into light, they will be weak trash.
i say to prune, but be conservative the first few attempts... once you watch one bloom and what's mor elikely to grwo intoa strong vertical cola, the better you can decide early and avoid wasted resources, which improves rate of growth and yield in the end.
you don't have to bend it in one spot... you may find a littlel roll between your finger and thumb further along helps it out too. you dn't have to 'supercrop' to get it level.