Looks like you buried it pretty deep but i don't see a problem. You may need more side room as they grow out.

you can prune (if you want to) to have one main trunk

Burying tomato deep should not cause a problem and maybe it can be a plus, as more root should grow from the buried pat.
Your plant looks ok but seems to be a bit pale. It could be the camera lighting or shortage of nitrogen/ too much water.

Sey

Pretty common appearance IMO. Doesn't really matter which is the "main stem" unless you only want 1 stem for some reason.

Dave

Thanks everyone, I guess I don't need to worry about it...