You can try to tap the boards together with a hammer and the pry tool that you used to install the boards. However, that only really works if the boards are properly connected but not fully seated.

It looks like the two in the pic are not connected at all and they're just sitting next to each other. In that case you'd have to disassemble the floor and make sure to attach them correctly. It's not terribly time consuming if you don't have to cut any new pieces.