Blue Tit Fledgling in Garden - Help Needed Please

I came across the sweetest blue tit fledgling in our garden today. They were able to fly a little, though seemed slightly panicked and as though they were trying to hide away. I really didn’t want to intervene, but we have two large dogs and often large birds such as magpies and seagulls in/around our garden, which I know can be a threat to young birds. We have numerous bird boxes located around our garden, and have seen the tits nesting in a couple of them, and so in a moment of panic, I thought it was the best idea to place the fledgling in one of the boxes. I didn’t know which box, if any, he/she came from and so I placed them in one of the more ‘central’ ones, which appears to be empty. There has been a lot of activity in one of the nearby boxes, but I haven’t seen any activity around the box I placed the fledgling in. I placed them in there a few hours ago now and I’m really regretting my decision, I feel as though I’ve done the wrong thing.

Does anybody have any suggestions at all as to what I should do?