I'm an idiot. Timber decking laid without gaps. Help!

[sxturbo]

If the wood has swelled that much leave the decking as is.

The recommended gap is 4mm anyway, so as the boards dry you'll get your gap.

Just keep an eye on it.

The guy who helped you do it, never ask him for help again, clearly he didn't have a clue what he was doing either

 

[big-all]

whilst a board can feel dry that is only the surface it can still be sodden underneath
indeed it can be quite a slow process to season timber takes months in the dry

 

[DIYSOS2018]

I’d leave it be and see what happens as it dries out. Sounds as though even though you’ve made a backside of it with the dampness of the boards you might be fine