Dahlia!

My first dahlia! Is it ok for there to be two main shoots growing from the tuber? Or should I remove the smaller one?

 

You can leave them intact or pinch out the tips of the taller shoot. It will be fine either way

 

I would keep both - but then, I'm an optimist and only have two years of experience to draw upon

Both look very healthy!

How old is the tuber?
Is it one you have over wintered? Or, one you have recently bought?

 

Leave both if you want more flowers.
Probably an exhibionist would just keep the one strong one.

 

It was a small tuber from s cheal multipack in home bargains! I’ve planted a few up.... umm... the ones outside aren’t growing so I’ll bring them in!

Is that single, humble tuber going to make a decent shrub this summer?

 

Thank you for clarifying
If the ones you have had outside haven't already succumbed to a hard frost, bringing them indoors might just be the saving grace. However, don't hold your breath Much depends on how cold your overnight temperatures have been.

If successful, yes, that one single, humble, tuber would indeed put on a good show this season.

Just something to consider though: I've bought tubers from el cheaper shops this year (first time too) and, so far, the multi packs (e.g. those packs with 3 in) are doing great - the single one is a massive fail as far as I can see. Very much a hit and miss affair!

Do bring in the ones you've planted outside and keep that the colder night temps haven't set them back/killed them off.

As for the one in the picture, continue to nurture it and it will reward you with multiple blooms later in the season

 

Yes Kriss but pinch it back a little.
To repeat, keep both shoots.
Temperatures are on the rise now and those shoots will grow quickly now. I would repot when the roots fill that pot to keep it growing well. By summer you will have bushy colourful plant